Magnetic head for perpendicular magnetic recording having a write shield

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system, and more specifically, to a magnetic head for perpendicular magnetic recording that has a write shield.

[0003] 2. Description of Related Art

[0004] The recording systems of magnetic recording devices such as magnetic disk drives include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of a recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of a recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.

[0005] Magnetic heads for perpendicular magnetic recording typically have, like those for longitudinal magnetic recording, a structure where a read head unit having a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head unit having an induction-type electromagnetic transducer for writing are stacked. The write head unit includes a main pole that produces a write magnetic field in a direction perpendicular to the plane of a recording medium.

[0006] In a magnetic disk drive, the magnetic head is mounted on a slider that flies slightly above the surface of a recording medium. The magnetic head has a medium facing surface to face the surface of the recording medium. The recording medium includes a magnetic recording layer. Tracks are concentrically formed in the magnetic recording layer. The tracks are the area of the magnetic recording layer on which data is to be written.

[0007] Here, the side of positions closer to a leading end relative to a reference position will be defined as the leading side, and the side of positions closer to a trailing end relative to the reference position will be defined as the trailing side. The leading side is the rear side in the direction of travel of the recording medium relative to the slider. The trailing side is the front side in the direction of travel of the recording medium relative to the slider.

[0008] The magnetic head is typically disposed near the trailing end of the medium facing surface of the slider. In a magnetic disk drive, positioning of the magnetic head is performed by a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit about the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs according to the position of the magnetic head across the tracks.

[0009] In particular, in a magnetic disk drive of the perpendicular magnetic recording system which is higher in capability of writing on a recording medium than the longitudinal magnetic recording system, the skew mentioned above can cause the phenomenon that signals already written on one or more tracks in the neighborhood of a track targeted for writing are erased or attenuated during writing of a signal on the track targeted for writing. In the present application, this phenomenon will be called unwanted erasure. Unwanted erasure includes adjacent track erasure (ATE) and wide-area track erasure (WATE). To achieve higher recording density, it is necessary to prevent unwanted erasure.

[0010] In order to prevent unwanted erasure induced by the skew and achieve higher recording density, it is effective to provide a write shield in the vicinity of the main pole. For example, U.S. Patent Application Publication No. 2005/0128637 A1 discloses a magnetic head having a write shield (a first side shorting shield, a second side shorting shield, a top shorting shield, and a bottom shorting shield) that has an end face wrapping around an end face of the main pole in the medium facing surface. Further, U.S. Pat. No. 7,365,943 B2 discloses a magnetic head having a write shield (a shield yoke) that has end faces located on opposite sides of the end face of the main pole in the track width direction in the medium facing surface.

[0011] The write shield has the function of capturing a magnetic flux that is produced from the end face of the main pole and spreads in directions other than the direction perpendicular to the plane of the recording medium, so as to prevent the magnetic flux from reaching the recording medium. A magnetic head having the write shield is capable of preventing unwanted erasure and capable of providing further improved recording density.

[0012] To make full use of the function of the write shield, it is preferred to provide a return path section for connecting the write shield and part of the main pole away from the medium facing surface to each other. The write shield and the return path section allow a magnetic flux that has been produced from the end face of the main pole and has magnetized the recording medium to flow back to the main pole. In the magnetic head disclosed in U.S. Patent Application Publication No. 2005/0128637 A1, a first return pole located on the trailing side relative to the main pole and a second return pole located on the leading side relative to the main pole constitute the aforementioned return path section.

[0013] The magnetic head disclosed in U.S. Pat. No. 7,365,943 B2 is provided with a return yoke connected to part of the main pole away from the medium facing surface. However, the write shield (the shield yoke) is not connected to the return yoke. In this magnetic head, the write shield is prone to flux saturation and thus it is difficult to make full use of the function of the write shield.

[0014] In a magnetic head having the write shield and the return path section, there is a space defined by the main pole, the write shield and the return path section. A coil is provided to pass through the space. The coil is driven by a write signal.

[0015] To prevent unwanted erasure, it is particularly important to capture a sufficient amount of magnetic flux into the write shield from two portions of the end face of the write shield that are located on opposite sides of the end face of the main pole in the track width direction, and to keep the magnetic flux having been captured into the write shield from leaking out of the write shield.

[0016] In the magnetic head disclosed in U.S. Patent Application Publication No. 2005/0128637 A1, a magnetic flux having been captured into the write shield from each of the two portions of the end face of the write shield that are located on opposite sides of the end face of the main pole in the track width direction bifurcates into two separate flows: one toward the first return pole located on the trailing side relative to the main pole; and the other toward the second return pole located on the leading side relative to the main pole. At this time, the magnetic flux passes through a magnetic path composed of a plurality of magnetic layers stacked one on another. The magnetic path includes one or more boundaries between two adjacent magnetic layers, the one or more boundaries being exposed in the medium facing surface. In the vicinity of the one or more boundaries, magnetic flux tends to leak from within the magnetic path to the outside thereof. This may result in the occurrence of unwanted erasure.

[0017] It is an object of the present invention to provide a magnetic head for perpendicular magnetic recording that makes it possible to make full use of the function of the write shield and prevent unwanted erasure, and to provide a head assembly and a magnetic recording device that each include such a magnetic head.

[0018] A magnetic head for perpendicular magnetic recording of the present invention includes: a medium facing surface that faces a recording medium; a coil that produces a magnetic field corresponding to data to be written on the recording medium; a main pole; a write shield made of a magnetic material; a gap part made of a nonmagnetic material; and a return path section made of a magnetic material. The main pole has an end face located in the medium facing surface. The main pole allows a magnetic flux corresponding to the magnetic field produced by the coil to pass, and produces a write magnetic field for writing the data on the recording medium by means of a perpendicular magnetic recording system. The write shield has an end face located in the medium facing surface. The gap part is interposed between the main pole and the write shield. The return path section connects the write shield and part of the main pole away from the medium facing surface to each other.

[0019] The end face of the write shield includes a first end face portion and a second end face portion located on opposite sides of the end face of the main pole in the track width direction. The write shield includes a first shield portion and a second shield portion located on opposite sides of the main pole in the track width direction. The first shield portion has the first end face portion. The second shield portion has the second end face portion. The return path section includes a first yoke portion and a second yoke portion located on opposite sides of the main pole in the track width direction. The first yoke portion is connected to the first shield portion so that a first space is defined by the main pole, the gap part, the first shield portion and the first yoke portion. The second yoke portion is connected to the second shield portion so that a second space is defined by the main pole, the gap part, the second shield portion and the second yoke portion. The coil passes through the first and second spaces so as to surround at least part of the entire outer periphery of the main pole when viewed from the medium facing surface. The first shield portion includes a portion located between the first space and the medium facing surface. The second shield portion includes a portion located between the second space and the medium facing surface.

[0020] In the magnetic head of the present invention, the write shield may include a portion that is located farther from the main pole in the track width direction than are one or more interfaces between the write shield and the return path section. Furthermore, the first shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section, and the second shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section.

[0021] In the magnetic head of the present invention, the end face of the write shield may further include a third end face portion located on the front side in the direction of travel of the recording medium relative to the end face of the main pole, and the write shield may further include a third shield portion located on the front side in the direction of travel of the recording medium relative to the main pole. The third shield portion has the third end face portion.

[0022] Where the write shield includes the third shield portion, the third shield portion may include a portion that is located farther from the main pole in the track width direction than are one or more interfaces between the write shield and the return path section. Furthermore, the first shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section, and the second shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section.

[0023] Where the write shield includes the third shield portion, the return path section may further include a third yoke portion located on the front side in the direction of travel of the recording medium relative to the main pole. The third yoke portion is connected to the third shield portion so that a third space is defined by the main pole, the gap part, the third shield portion and the third yoke portion. The coil may pass through the third space.

[0024] In the magnetic head of the present invention, the end face of the write shield may further include a fourth end face portion located on the rear side in the direction of travel of the recording medium relative to the end face of the main pole, and the write shield may further include a fourth shield portion located on the rear side in the direction of travel of the recording medium relative to the main pole. The fourth shield portion has the fourth end face portion.

[0025] Where the write shield includes the fourth shield portion, the fourth shield portion may include a portion that is located farther from the main pole in the track width direction than are one or more interfaces between the write shield and the return path section. Furthermore, the first shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section, and the second shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section.

[0026] Where the write shield includes the fourth shield portion, the return path section may further include a fourth yoke portion located on the rear side in the direction of travel of the recording medium relative to the main pole. The fourth yoke portion is connected to the fourth shield portion so that a fourth space is defined by the main pole, the gap part, the fourth shield portion and the fourth yoke portion. The coil may pass through the fourth space.

[0027] In the magnetic head of the present invention, the end face of the write shield may further include a third end face portion located on the front side in the direction of travel of the recording medium relative to the end face of the main pole, and a fourth end face portion located on the rear side in the direction of travel of the recording medium relative to the end face of the main pole. Furthermore, the write shield may further include a third shield portion located on the front side in the direction of travel of the recording medium relative to the main pole, and a fourth shield portion located on the rear side in the direction of travel of the recording medium relative to the main pole. The third shield portion has the third end face portion, and the fourth shield portion has the fourth end face portion.

[0028] Where the write shield includes the third and fourth shield portions, at least one of the third and fourth shield portions may include a portion that is located farther from the main pole in the track width direction than are one or more interfaces between the write shield and the return path section. Furthermore, the first shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section, and the second shield portion may further include a portion that is located farther from the main pole in the track width direction than are the one or more interfaces between the write shield and the return path section.

[0029] Where the write shield includes the third and fourth shield portions, the return path section may further include a third yoke portion located on the front side in the direction of travel of the recording medium relative to the main pole, and a fourth yoke portion located on the rear side in the direction of travel of the recording medium relative to the main pole. The third yoke portion is connected to the third shield portion so that a third space is defined by the main pole, the gap part, the third shield portion and the third yoke portion. The fourth yoke portion is connected to the fourth shield portion so that a fourth space is defined by the main pole, the gap part, the fourth shield portion and the fourth yoke portion. The coil may pass through at least one of the third space and the fourth space.

[0030] Further, in the magnetic head of the present invention, the coil may not wrap one turn around the entire outer periphery of the main pole. In this case, of the entire outer periphery of the main pole when viewed from the medium facing surface, the coil may surround a portion located on the front side or the rear side in the direction of travel of the recording medium and portions located on opposite sides in the track width direction. Further, the distance from the medium facing surface to one of edges of one or more interfaces between the main pole and the return path section, the one of the edges being closest to the medium facing surface, may fall within the range of 1.0 to 2.5 μm.

[0031] A head assembly of the present invention includes a slider, and a supporter that flexibly supports the slider. The slider includes the magnetic head of the present invention and is disposed to face a recording medium.

[0032] A magnetic recording device of the present invention includes the magnetic head of the present invention, a recording medium, and a positioning device that supports the magnetic head and positions the magnetic head with respect to the recording medium.

[0033] In the magnetic head of the present invention, the write shield includes the first and second shield portions located on opposite sides of the main pole in the track width direction, and the return path section includes the first and second yoke portions located on opposite sides of the main pole in the track width direction. The coil passes through the first and second spaces so as to surround at least part of the entire outer periphery of the main pole when viewed from the medium facing surface. Thus, according to the magnetic head of the present invention, and the head assembly and the magnetic recording device including this magnetic head, it is possible to make full use of the function of the write shield and to prevent unwanted erasure.

[0034] Other objects, features and advantages of the present invention will become fully apparent from the following description.

[0082] Embodiments of the present invention will now be described in detail with reference to the drawings. First, reference is made to FIG. 7 to describe a slider 210 including a magnetic head according to a first embodiment of the invention. The magnetic head according to the present embodiment is for use in perpendicular magnetic recording. In a magnetic recording device, the slider 210 is disposed to face a circular-plate-shaped recording medium (a magnetic disk) that is driven to rotate. In FIG. 7, the X direction is a direction across the tracks of the recording medium, i.e., the track width direction. The Y direction is a direction perpendicular to the surface of the recording medium. The Z direction is the direction of travel of the recording medium when viewed from the slider 210. The X, Y, and Z directions are orthogonal to one another. The slider 210 has a base body 211. The base body 211 is generally hexahedron-shaped. One of the six surfaces of the base body 211 is designed to face the surface of the recording medium. At this one of the six surfaces, there is formed a medium facing surface 40 to face the surface of the recording medium. When the recording medium rotates and travels in the Z direction, an airflow passing between the recording medium and the slider 210 causes a lift below the slider 210 in the Y direction of FIG. 7. The lift causes the slider 210 to fly over the surface of the recording medium. The magnetic head 100 according to the present embodiment is formed near the air-outflow-side end (the end in the Z direction) of the slider 210. A plurality of terminals 212 are also provided at the air-outflow-side end of the slider 210.

[0083] A head assembly according to the present embodiment will now be described with reference to FIG. 8. The head assembly according to the present embodiment includes the slider 210 shown in FIG. 7 and a supporter that flexibly supports the slider 210. Forms of the head assembly include a head gimbal assembly and a head arm assembly described below.

[0084] The head gimbal assembly 220 will be described first. The head gimbal assembly 220 includes the slider 210, and a suspension 221 serving as the supporter that flexibly supports the slider 210. The suspension 221 includes: a plate-spring-shaped load beam 222 formed of, e.g., stainless steel; a flexure 223 to which the slider 210 is joined, the flexure 223 being provided at an end of the load beam 222 and giving an appropriate degree of freedom to the slider 210; and a base plate 224 provided at the other end of the load beam 222. The base plate 224 is configured to be attached to an arm 230 of an actuator for moving the slider 210 along the X direction across the tracks of the recording medium 262. The actuator has the arm 230 and a voice coil motor that drives the arm 230. A gimbal section for maintaining the orientation of the slider 210 is provided in the portion of the flexure 223 on which the slider 210 is mounted.

[0085] The head gimbal assembly 220 is attached to the arm 230 of the actuator. An assembly including the arm 230 and the head gimbal assembly 220 attached to the arm 230 is called a head arm assembly. An assembly including a carriage having a plurality of arms with a plurality of head gimbal assemblies 220 respectively attached to the arms is called a head stack assembly.

[0086] FIG. 8 shows the head arm assembly according to the present embodiment. In the head arm assembly, the head gimbal assembly 220 is attached to an end of the arm 230. A coil 231 that forms part of the voice coil motor is fixed to the other end of the arm 230. A bearing 233 is provided in the middle of the arm 230. The bearing 233 is attached to a shaft 234 for rotatably supporting the arm 230.

[0087] Reference is now made to FIG. 9 and FIG. 10 to describe an example of the head stack assembly and an example of a magnetic recording device according to the present embodiment. FIG. 9 is an explanatory diagram illustrating the main part of the magnetic recording device. FIG. 10 is a plan view of the magnetic recording device. The head stack assembly 250 includes a carriage 251 having a plurality of arms 252. A plurality of head gimbal assemblies 220 are attached to the arms 252 such that the assemblies 220 are aligned in the vertical direction with spacing between every adjacent ones. A coil 253 forming part of the voice coil motor is mounted on a side of the carriage 251 opposite from the arms 252. The head stack assembly 250 is installed in the magnetic recording device. The magnetic recording device includes a plurality of recording media 262 mounted on a spindle motor 261. Two sliders 210 are allocated to each recording medium 262 such that the two sliders 210 are opposed to each other with the recording medium 262 interposed therebetween. The voice coil motor includes permanent magnets 263 arranged to be opposed to each other with the coil 253 of the head stack assembly 250 interposed therebetween. The actuator and the head stack assembly 250 except the sliders 210 support the sliders 210 and position them with respect to the recording media 262. Note that the magnetic recording device of the present invention may be configured otherwise than the above-described configuration. For example, the magnetic recording device of the present invention may be provided with a single recording medium 262 and one or two head gimbal assemblies 220.

[0088] In the magnetic recording device according to the present embodiment, the actuator moves the slider 210 across the tracks of the recording medium 262 and positions the slider 210 with respect to the recording medium 262. The magnetic head 100 included in the slider 210 has a read head unit and a write head unit, which will be described in detail later.

[0089] Reference is now made to FIG. 1 to FIG. 3 to describe the general configuration of the magnetic head according to the present embodiment, particularly the general configuration of the write head unit. FIG. 1 is a perspective view showing the main part of the magnetic head. FIG. 2 is a perspective view showing the main part shown in FIG. 1 with some portions eliminated. FIG. 3 is a plan view showing the main part shown in FIG. 1 with some other portions eliminated. The X, Y, and Z directions shown in FIG. 7 are also shown in FIG. 1 to FIG. 3.

[0090] As shown in FIG. 1 and FIG. 3, the magnetic head according to the present embodiment has the medium facing surface 40. The write head unit includes a coil 111, leads 112 and 113, a main pole 25, a write shield 120, a gap part 130, and a return path section 140. FIG. 2 omits the write shield 120. FIG. 3 omits respective portions of the coil 111 and the return path section 140 that are located on the trailing side relative to the main pole 25.

[0091] The write shield 120 and the return path section 140 form one or more interfaces B1 therebetween. In the present embodiment, in particular, the write shield 120 and the return path section 140 form two interfaces B1 therebetween. FIG. 1 and FIG. 3 show the two interfaces B1 between the write shield 120 and the return path section 140 by broken lines. Further, the main pole 25 and the return path section 140 form one or more interfaces B2 therebetween. In the present embodiment, in particular, the main pole 25 and the return path section 140 form four interfaces B2 therebetween. FIG. 3 shows two of the four interfaces B2 between the main pole 25 and the return path section 140 by solid lines.

[0092] The main pole 25 has an end face located in the medium facing surface 40, and a top surface. In the present embodiment, the main pole 25 includes a track width defining portion 25A and a wide portion 25B, in particular. The track width defining portion 25A has an end face located in the medium facing surface, and an end portion opposite to the end face. The wide portion 25B is connected to the end portion of the track width defining portion 25A. The top surface of the main pole 25 includes a top surface of the track width defining portion 25A and a top surface of the wide portion 25B. The top surface of the wide portion 25B is greater than the top surface of the track width defining portion 25A in width in the track width direction.

[0093] The width of the top surface of the track width defining portion 25A in the track width direction is generally constant regardless of the distance from the medium facing surface 40. The width of the top surface of the wide portion 25B in the track width direction is, for example, equal to that of the top surface of the track width defining portion 25A when seen at the boundary between the track width defining portion 25A and the wide portion 25B, and gradually increases with increasing distance from the medium facing surface 40, then becoming constant. Note that the track width defining portion 25A may be omitted to configure the wide portion 25B to have an end face located in the medium facing surface 40. Further, relative to a direction perpendicular to the medium facing surface 40, two edges of the top surface of the wide portion 25B that are opposite in the track width direction may each form an angle that is constant regardless of the distance from the medium facing surface 40 or that varies with distance from the medium facing surface 40. The thickness of the main pole 25 in the vicinity of the medium facing surface 40 may decrease toward the medium facing surface 40.

[0094] The width of the end face of the main pole 25 located in the medium facing surface 40 decreases with increasing proximity to the leading-side end, for example. The position of the end of a record bit to be recorded on a recording medium depends on the position of the trailing-side edge of the end face of the main pole 25. FIG. 1 and FIG. 2 show an example in which the end face of the main pole 25 has a trapezoidal shape. However, the shape of the end face of the main pole 25 is not limited thereto, and may be, for example, square, rectangular, circular or elliptical. Alternatively, the end face of the main pole 25 may be in the shape of a pentagon with one vertex located at the leading-side end and one side located at the trailing-side end.

[0095] The write shield 120 has an end face located in the medium facing surface 40. As shown in FIG. 1, the end face of the write shield 120 includes first to fourth end face portions 121a, 122a, 123a, and 124a. The first and second end face portions 121a and 122a are located on opposite sides of the end face of the main pole 25 in the track width direction (the X direction). The third end face portion 123a is located on the front side in the direction of travel of the recording medium (the Z direction), i.e., the trailing side, relative to the end face of the main pole 25. The fourth end face portion 124a is located on the rear side in the direction of travel of the recording medium (the Z direction), i.e., the leading side, relative to the end face of the main pole 25. In the medium facing surface 40, the first to fourth end face portions 121a, 122a, 123a, and 124a are arranged to wrap around the end face of the main pole 25.

[0096] The write shield 120 includes first to fourth shield portions 121, 122, 123, and 124. In FIG. 1 the boundaries between these portions are shown by dotted lines. The first and second shield portions 121 and 122 are located on opposite sides of the main pole 25 in the track width direction. The third shield portion 123 is located on the front side in the direction of travel of the recording medium relative to the main pole 25. The fourth shield portion 124 is located on the rear side in the direction of travel of the recording medium relative to the main pole 25.

[0097] As shown in FIG. 1, the first shield portion 121 has the first end face portion 121a. The second shield portion 122 has the second end face portion 122a. The third shield portion 123 has the third end face portion 123a. The fourth shield portion 124 has the fourth end face portion 124a.

[0098] The gap part 130 is interposed between the main pole 25 and the write shield 120. The gap part 130 includes a first gap portion 130A interposed between the main pole 25 and each of the first, second and fourth shield portions 121, 122 and 124, and a second gap portion 130B interposed between the main pole 25 and the third shield portion 123. In the medium facing surface 40, the width of the second gap portion 130B in the track width direction is greater than the distance between the first shield portion 121 and the second shield portion 122. This is for the purpose of preventing the end of a record bit to be recorded on a recording medium from becoming arc-shaped.

[0099] The return path section 140 connects the write shield 120 and part of the main pole 25 away from the medium facing surface 40 to each other, thereby magnetically coupling the write shield 120 and the main pole 25 to each other. The return path section 140 includes first and second yoke portions 141 and 142, and first and second coupling portions 145 and 146. In FIG. 1 and FIG. 2 the boundaries between these portions are shown by dotted lines.

[0100] The first and second yoke portions 141 and 142 are located on opposite sides of the main pole 25 in the track width direction. As shown in FIG. 3, the first yoke portion 141 is connected to the first shield portion 121 so that a first space S1 is defined by the main pole 25, the gap part 130, the first shield portion 121 and the first yoke portion 141. Further, the second yoke portion 142 is connected to the second shield portion 122 so that a second space S2 is defined by the main pole 25, the gap part 130, the second shield portion 122 and the second yoke portion 142. The first shield portion 121 includes a portion located between the first space S1 and the medium facing surface 40. The second shield portion 122 includes a portion located between the second space S2 and the medium facing surface 40.

[0101] In the present embodiment, the first yoke portion 141 includes a portion 141A connected to the first shield portion 121, a portion 141B located on the front side in the direction of travel of the recording medium (the Z direction) relative to the portion 141A, and a portion 141C located on the rear side in the direction of travel of the recording medium relative to the portion 141A. Further, the second yoke portion 142 includes a portion 142A connected to the second shield portion 122, a portion 142B located on the front side in the direction of travel of the recording medium relative to the portion 142A, and a portion 142C located on the rear side in the direction of travel of the recording medium relative to the portion 142A. In FIG. 1 and FIG. 2 the boundaries between these portions are shown by chain double-dashed lines. The portions 141A and 142A are located at the same level as the first and second shield portions 121 and 122 in the direction of travel of the recording medium. The portions 141B and 142B are located at the same level as the third shield portion 123 in the direction of travel of the recording medium, and are connected to the third shield portion 123. The portions 141C and 142C are located at the same level as the fourth shield portion 124 in the direction of travel of the recording medium, and are connected to the fourth shield portion 124.

[0102] The first and second coupling portions 145 and 146 are located away from the medium facing surface 40. The first coupling portion 145 is located on the front side in the direction of travel of the recording medium relative to the main pole 25 and connected to the main pole 25, and couples the portion 141B of the first yoke portion 141 and the portion 142B of the second yoke portion 142 to each other. The second coupling portion 146 is located on the rear side in the direction of travel of the recording medium relative to the main pole 25 and connected to the main pole 25, and couples the portion 141C of the first yoke portion 141 and the portion 142C of the second yoke portion 142 to each other.

[0103] As shown in FIG. 1, where the write shield 120 includes the first to fourth shield portions 121, 122, 123 and 124, the first yoke portion 141 need only include one or more of the portions 141A, 141B and 141C, while the second yoke portion 142 need only include one or more of the portions 142A, 142B and 142C.

[0104] The write shield 120 may include only the first to third shield portions 121, 122 and 123. In this case, the first yoke portion 141 need only include at least one of the portions 141A and 141B, while the second yoke portion 142 need only include at least one of the portions 142A and 142B.

[0105] The write shield 120 may include only the first, second and fourth shield portions 121, 122 and 124. In this case, the first yoke portion 141 need only include at least one of the portions 141A and 141C, while the second yoke portion 142 need only include at least one of the portions 142A and 142C.

[0106] The write shield 120 may include only the first and second shield portions 121 and 122. In this case, the first yoke portion 141 includes at least the portion 141A, while the second yoke portion 142 includes at least the portion 142A.

[0107] Where the first yoke portion 141 does not include the portion 141B and the second yoke portion 142 does not include the portion 142B, the first coupling portion 145 may be omitted. Where the first yoke portion 141 does not include the portion 141C and the second yoke portion 142 does not include the portion 142C, the second coupling portion 146 may be omitted.

[0108] Here, as shown in FIG. 3, the distance from the medium facing surface 40 to one of edges of the one or more interfaces B2 between the main pole 25 and the return path section 140, the one of the edges being closest to the medium facing surface 40, will be defined as the yoke length and denoted by symbol YL. In the present embodiment, the yoke length YL is the shortest one of the distances from the medium facing surface 40 to respective ones of edges of the interfaces between: the main pole 25 and the yoke portion 141; the main pole 25 and the yoke portion 142; the main pole 25 and the coupling portion 145; and the main pole 25 and the coupling portion 146, the respective ones of the edges being closest to the medium facing surface 40. The aforementioned distances from the medium facing surface 40 to the respective ones of the edges of the interfaces between the main pole 25 and the portions 141, 142, 145, and 146 closest to the medium facing surface 40 may be equal to each other. The yoke length YL falls within the range of 1.0 to 2.5 μm, for example.

[0109] The coil 111 is located at a distance from the medium facing surface 40. The leads 112 and 113 are connected to opposite ends of the coil 111. The coil 111 and the leads 112 and 113 form one continuous conductor. Of this conductor, a portion located inwardly from the outer surface of an assembly consisting of the write shield 120 and the return path section 140 is the coil 111, whereas portions located outwardly from the aforementioned outer surface are the leads 112 and 113. In FIG. 1 and FIG. 2 the boundaries between the coil 111 and the leads 112 and 113 are indicated by dotted lines. In FIG. 3, the portion of the coil 111 located on the trailing side relative to the main pole 25 is shown in a chain double-dashed line. The coil 111 passes through the first and second spaces S1 and S2 so as to surround at least part of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40. In the present embodiment, as shown in FIG. 2, of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40, the coil 111 particularly surrounds a portion located on the front side in the direction of travel of the recording medium (the Z direction) and portions located on opposite sides in the track width direction (the X direction). Thus, the coil 111 does not wrap one turn around the entire outer periphery of the main pole 25. The leads 112 and 113 are located on the rear side in the direction of travel of the recording medium relative to the main pole 25 and drawn from opposite ends of the coil 111 in opposite directions along the track width.

[0110] The coil 111 and the leads 112 and 113 are made of a conductive material such as copper. The write shield 120 and the return path section 140 are each made of a magnetic material. The write shield 120 and the return path section 140 may be made of any of NiFe, CoFe, CoNiFe, CoNi, FeCo, and FeNi, for example. The gap part 130 is made of a nonmagnetic material such as alumina (Al₂O₃).

[0111] The configuration of the magnetic head according to the present embodiment will now be described in more detail with reference to FIG. 1 to FIG. 6. FIG. 4 is a cross-sectional view showing the configuration of the magnetic head. FIG. 5 is a front view showing the medium facing surface of the magnetic head. FIG. 6 is a cross-sectional view showing a cross section taken at the position indicated by line 6-6 of FIG. 4. The X, Y, and Z directions shown in FIG. 7 are also shown in FIG. 4 to FIG. 6.

[0112] As shown in FIG. 4 to FIG. 6, the magnetic head according to the present embodiment includes: a substrate 1 made of a ceramic material such as aluminum oxide-titanium carbide (Al₂O₃—TiC) and having a top surface; an insulating layer 2 made of an insulating material and disposed on the substrate 1; a bottom read shield layer 3 made of a magnetic material and disposed on the insulating layer 2; a magnetoresistive element (hereinafter referred to as MR element) 4 disposed on the bottom read shield layer 3; a top read shield layer 6 made of a magnetic material and disposed on the MR element 4; and an insulating layer 5 made of an insulating material, disposed between the bottom read shield layer 3 and the top read shield layer 6 and surrounding the MR element 4. The insulating layers 2 and 5 are made of alumina, for example. Note that FIG. 4 shows a cross section perpendicular to the medium facing surface 40 and to the top surface of the substrate 1.

[0113] An end of the MR element 4 is located in the medium facing surface 40. The MR element 4 may be a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR) element, for example. The GMR element may be of either the current-in-plane (CIP) type in which a sense current for use in magnetic signal detection is fed in a direction generally parallel to the planes of layers constituting the GMR element or the current-perpendicular-to-plane (CPP) type in which the sense current is fed in a direction generally perpendicular to the planes of layers constituting the GMR element. Where the MR element 4 is a TMR element or a CPP-type GMR element, the bottom read shield layer 3 and the top read shield layer 6 may also serve as electrodes for feeding the sense current to the MR element 4. Where the MR element 4 is a CIP-type GMR element, insulating films are respectively provided between the MR element 4 and the bottom read shield layer 3 and between the MR element 4 and the top read shield layer 6, and two leads are provided between these insulating films in order to feed the sense current to the MR element 4.

[0114] The parts from the bottom read shield layer 3 to the top read shield layer 6 constitute the read head unit. The magnetic head further includes: a nonmagnetic layer 71 made of an insulating material and disposed on the top read shield layer 6; a middle shield layer 72 made of a magnetic material and disposed on the nonmagnetic layer 71; an insulating layer 73 disposed on the middle shield layer 72; and the write head unit disposed on the insulating layer 73. The middle shield layer 72 has the function of shielding the MR element 4 from magnetic fields generated in the write head unit. The nonmagnetic layer 71 and the insulating layer 73 are made of alumina, for example. The write head unit includes the coil 111, the leads 112 and 113, the main pole 25, the write shield 120, the gap part 130, and the return path section 140. The coil 111 is composed of a plurality of conductive layers described later.

[0115] As shown in FIG. 6, the magnetic head further includes two conductive layers 13 and 14 made of a conductive material and disposed on the insulating layer 73, and an insulating layer 17 disposed on the insulating layer 73 and surrounding the conductive layers 13 and 14. The conductive layer 13 forms the lead 112 and a part of the coil 111. The conductive layer 14 forms the lead 113 and another part of the coil 111. The insulating layer 17 is made of alumina, for example.

[0116] As shown in FIG. 6, the magnetic head further includes an insulating layer 18 disposed on the conductive layers 13 and 14 and the insulating layer 17, and conductive layers 20 and 21 made of a conductive material. The insulating layer 18 has a first opening for exposing a portion of the top surface of the conductive layer 13 near an edge thereof closest to the conductive layer 14, and a second opening for exposing a portion of the top surface of the conductive layer 14 near an edge thereof closest to the conductive layer 13. The conductive layer 20 lies on the conductive layer 13 at the position of the first opening of the insulating layer 18. The conductive layer 21 lies on the conductive layer 14 at the position of the second opening of the insulating layer 18. Each of the conductive layers 20 and 21 forms another part of the coil 111. The insulating layer 18 is made of alumina, for example.

[0117] As shown in FIG. 4 and FIG. 5, the magnetic head further includes a magnetic layer 19 made of a magnetic material. The magnetic layer 19 includes a first portion 19A and a second portion 19B. The first portion 19A forms the first, second and fourth shield portions 121, 122 and 124. The second portion 19B forms the portions 141A and 141C of the first yoke portion 141, the portions 142A and 142C of the second yoke portion 142, and the second coupling portion 146. The first portion 19A and the second portion 19B are both located on the insulating layer 18. The first portion 19A is shaped to be elongated in the X direction. The second portion 19B is connected to portions of the first portion 19A adjacent to opposite ends thereof in the X direction so that a space is defined by the first portion 19A and the second portion 19B. As shown in FIG. 6, the conductive layers 20 and 21 are disposed in the space. The insulating layer 18 is interposed between the second portion 19B and each of the conductive layers 13 and 14.

[0118] A portion of the main pole 25 in the vicinity of the medium facing surface 40 is located at a predetermined distance from the first, second and fourth shield portions 121, 122 and 124 formed by the first portion 19A. A portion of the main pole 25 away from the medium facing surface 40 is in contact with the second portion 19B. As shown in FIG. 6, the conductive layers 20 and 21 are located on opposite sides of the main pole 25 in the track width direction (the X direction) and are each separated from the main pole 25.

[0119] The magnetic head further includes a nonmagnetic layer 24 made of an insulating nonmagnetic material and disposed around the magnetic layer 19, the conductive layers 20 and 21 and the main pole 25. The nonmagnetic layer 24 is interposed between the second portion 19B and each of the conductive layers 20 and 21. The top surfaces of the magnetic layer 19, the conductive layers 20 and 21, the main pole 25 and the nonmagnetic layer 24 are even with each other. A portion of the nonmagnetic layer 24 that is interposed between the main pole 25 and the first portion 19A of the magnetic layer 19 forms the first gap portion 130A. The nonmagnetic layer 24 is made of alumina, for example.

[0120] As shown in FIG. 4 and FIG. 6, the magnetic head further includes a nonmagnetic layer 26 made of an insulating nonmagnetic material and lying on the first portion 19A of the magnetic layer 19, the main pole 25 and the nonmagnetic layer 24, and a conductive layer 28 made of a conductive material and lying on the nonmagnetic layers 24 and 26 and the conductive layers 20 and 21. The nonmagnetic layer 26 does not cover a portion of the top surface of the main pole 25 located away from the medium facing surface 40.

[0121] As shown in FIG. 6, the conductive layer 28 is shaped to be elongated in the X direction. A portion of the conductive layer 28 adjacent to its one end in the longitudinal direction is in contact with the conductive layer 20, and a portion of the conductive layer 28 adjacent to its other end in the longitudinal direction is in contact with the conductive layer 21. The conductive layer 28 forms the remaining part of the coil 111. The nonmagnetic layer 26 is interposed between the conductive layer 28 and the main pole 25. The nonmagnetic layer 26 is made of alumina, for example.

[0122] The magnetic head further includes a magnetic layer 27 made of a magnetic material. The magnetic layer 27 includes a first portion 27A forming the third shield portion 123, and a second portion 27B forming the portion 141B of the first yoke portion 141, the portion 142B of the second yoke portion 142 and the first coupling portion 145. The first portion 27A is shaped to be elongated in the X direction and lies on the first portion 19A of the magnetic layer 19 and the nonmagnetic layer 26. The second portion 27B lies on the second portion 19B of the magnetic layer 19 and the main pole 25. The second portion 27B is connected to portions of the first portion 27A adjacent to opposite ends thereof in the X direction so that a space is defined by the first portion 27A and the second portion 27B. As shown in FIG. 6, the conductive layer 28 is disposed in the space.

[0123] A portion of the nonmagnetic layer 26 that is interposed between the main pole 25 and the first portion 27A (the third shield portion 123) forms the second gap portion 130B. In the medium facing surface 40, a portion of the end face of the first portion 27A (the third end face portion 123a) is separated from the end face of the main pole 25 by a predetermined distance created by the thickness of the second gap portion 130B. The thickness of the second gap portion 130B is preferably 200 nm or smaller, and more preferably falls within the range of 15 to 50 nm.

[0124] The magnetic head further includes an insulating layer 32 disposed on the nonmagnetic layer 26 and surrounding the magnetic layer 27 and the conductive layer 28. The top surfaces of the magnetic layer 27, the conductive layer 28 and the insulating layer 32 are even with each other. The insulating layer 32 is made of alumina, for example.

[0125] The magnetic head further includes a protective layer 36 made of an insulating material such as alumina and disposed to cover the write head unit. The base body 211 shown in FIG. 7 is mainly composed of the substrate 1 and the protective layer 36 shown in FIG. 4 to FIG. 6.

[0126] As has been described, the magnetic head according to the present embodiment has the medium facing surface 40, the read head unit, and the write head unit. The read head unit and the write head unit are stacked on the substrate 1. The read head unit is located on the rear side in the direction of travel of the recording medium (the Z direction), i.e., the leading side, relative to the write head unit.

[0127] The write head unit includes the coil 111, the leads 112 and 113, the main pole 25, the write shield 120, the gap part 130, and the return path section 140. The coil 111 is composed of portions of the conductive layers 13 and 14, and the conductive layers 20, 21 and 28. The leads 112 and 113 are composed of the remaining portions of the conductive layers 13 and 14. The write shield 120 includes the first to fourth shield portions 121 to 124. The gap part 130 includes the first and second gap portions 130A and 130B. The return path section 140 includes the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146.

[0128] The function and effects of the magnetic head according to the present embodiment will now be described. The magnetic head writes data on a recording medium by using the write head unit and reads data stored on a recording medium by using the read head unit. In the write head unit, the coil 111 produces a magnetic field corresponding to data to be written on a recording medium. The main pole 25 allows a magnetic flux corresponding to the magnetic field produced by the coil 111 to pass, and produces a write magnetic field for writing data on the recording medium by means of a perpendicular magnetic recording system.

[0129] The write shield 120 captures a disturbance magnetic field applied to the magnetic head from the outside thereof. This prevents the disturbance magnetic field from being intensively captured into the main pole 25 and inducing erroneous writing on a recording medium. Further, the write shield 120 has the function of capturing a magnetic flux that is produced from the end face of the main pole 25 and spreads in directions other than the direction perpendicular to the plane of the recording medium, so as to prevent the magnetic flux from reaching the recording medium. Moreover, the write shield 120 and the return path section 140 have the function of allowing a magnetic flux that has been produced from the end face of the main pole 25 and has magnetized the recording medium to flow back to the main pole 25.

[0130] In the present embodiment, the write shield 120 includes the first and second shield portions 121 and 122 located on opposite sides of the main pole 25 in the track width direction, and the return path section 140 includes the first and second yoke portions 141 and 142 located on opposite sides of the main pole 25 in the track width direction. The coil 111 passes through the first and second spaces S1 and S2 so as to surround at least part of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40. The present embodiment having these features makes it possible to make full use of the function of the write shield 120 and to prevent unwanted erasure. This advantageous effect will be described in detail below.

[0131] In the present embodiment, a magnetic flux having been captured into the first shield portion 121 flows toward the first yoke portion 141, while a magnetic flux having been captured into the second shield portion 122 flows toward the second yoke portion 142. More specifically, in the present embodiment, the magnetic fluxes having been captured into the first and second shield portions 121 and 122 located on opposite sides of the main pole 25 in the track width direction flow smoothly, with hardly any restriction imposed by the magnetic path structure, toward the first and second yoke portions 141 and 142 located on opposite sides of the main pole 25 in the track width direction, and flow back to the main pole 25. Thus, the present embodiment makes it possible to capture a sufficient amount of magnetic flux into the write shield 120 from the first and second shield portions 121 and 122, and prevent the magnetic flux having been captured into the write shield 120 from leaking out of the write shield 120. Consequently, according to the present embodiment, it is possible to make full use of the function of the write shield 120 and to prevent unwanted erasure.

[0132] Now, a magnetic head of a first comparative example having the following configuration will be contemplated for comparison with the magnetic head according to the present embodiment. The magnetic head of the first comparative example does not have the first and second yoke portions 141 and 142 of the first embodiment, and instead has a first return yoke located on the trailing side relative to the main pole 25 and connected to the write shield 120, a second return yoke located on the leading side relative to the main pole 25 and connected to the write shield 120, a first coupling part coupling the first return yoke to part of the main pole 25 away from the medium facing surface 40, and a second coupling part coupling the second return yoke to part of the main pole 25 away from the medium facing surface 40. Further, the magnetic head of the first comparative example has a coil having a first winding portion wound around the first coupling part and a second winding portion wound around the second coupling part, in place of the coil 111 of the first embodiment. U.S. Patent Application Publication No. 2005/0128637 A1 discloses a magnetic head having a configuration similar to that of the magnetic head of the first comparative example.

[0133] In the magnetic head of the first comparative example, a magnetic flux having been captured into each of the first and second shield portions 121 and 122 located on opposite sides of the main pole 25 in the track width direction bifurcates into two separate flows: one toward the first return yoke; and the other toward the second return yoke. At this time, the magnetic flux passes through a magnetic path composed of a plurality of magnetic layers stacked one on another. The magnetic path includes one or more boundaries between two adjacent magnetic layers, the one or more boundaries being exposed in the medium facing surface 40. In the vicinity of the one or more boundaries, magnetic flux tends to leak from within the magnetic path to the outside thereof. This may result in the occurrence of unwanted erasure. The occurrence of unwanted erasure may become noticeable particularly when the two adjacent magnetic layers are made of different materials.

[0134] In contrast to this, the magnetic head according to the present embodiment is configured so that neither the magnetic path passing through the first shield portion 121 and the first yoke portion 141 nor the magnetic path passing through the second shield portion 122 and the second yoke portion 142 includes any boundary between two magnetic layers that is exposed in the medium facing surface 40. Thus, the present embodiment makes it possible to prevent the occurrence of unwanted erasure resulting from a boundary between two magnetic layers.

[0135] Now, a comparison will be made between the operation of the magnetic head of the first comparative example and that of the magnetic head according to the present embodiment when the width of the second gap portion 130B in the track width direction is greater than the distance between the first shield portion 121 and the second shield portion 122 in the medium facing surface 40, as shown in FIG. 5. In the magnetic head of the first comparative example, as described above, a magnetic flux having been captured into each of the first and second shield portions 121 and 122 bifurcates into two separate flows: one toward the first return yoke; and the other toward the second return yoke. The flow of the magnetic flux toward the first return yoke from each of the first and second shield portions 121 and 122 is restricted on the way by the second gap portion 130B which is large in width in the track width direction. Thus, in the vicinity of the second gap portion 130B, the magnetic flux tends to leak from within the write shield 120 to the outside thereof. This may result in the occurrence of unwanted erasure.

[0136] In contrast to this, in the magnetic head according to the present embodiment, magnetic fluxes having been captured into the first and second shield portions 121 and 122 flow toward the first and second yoke portions 141 and 142, respectively, as described above. Therefore, the flows of the magnetic fluxes will not be restricted by the second gap portion 130B. Thus, according to the present embodiment, it is possible to prevent the occurrence of unwanted erasure attributable to the second gap portion 130B.

[0137] Now, consider a magnetic head of a second comparative example having such a structure that the first and second yoke portions 141 and 142 are added to the magnetic head of the first comparative example. In the magnetic head of the second comparative example, a magnetic flux corresponding to a magnetic field produced by the first winding portion trifurcates into three separate flows: one from the first coupling part toward the main pole 25; another from the first coupling part toward the first yoke portion 141; and the other from the first coupling part toward the second yoke portion 142. Likewise, a magnetic flux corresponding to a magnetic field produced by the second winding portion trifurcates into three separate flows: one from the second coupling part toward the main pole 25; another from the second coupling part toward the first yoke portion 141; and the other from the second coupling part toward the second yoke portion 142. As a result, magnetic fields are produced from the first and second end faces 121a and 122a in a direction the same as the direction of the write magnetic field produced from the end face of the main pole 25. This causes the problem of unwanted erasure to arise with the magnetic head of the second comparative example.

[0138] In contrast to this, in the magnetic head according to the present embodiment, since the coil 111 is wound around the main pole 25, magnetic fields produced from the first and second end faces 121a and 122a are in the opposite direction to the direction of the write magnetic field produced from the end face of the main pole 25. The present embodiment is thus free from the aforementioned problem with the second comparative example.

[0139] As can be seen from the foregoing, the present embodiment makes it possible to make full use of the function of the write shield 120 and to prevent unwanted erasure. Simulation results showing this effect will be described later.

[0140] A second embodiment of the present invention will now be described with reference to FIG. 11 and FIG. 12. FIG. 11 is a perspective view showing the main part of the magnetic head. FIG. 12 is a plan view showing the main part shown in FIG. 11 with some portions eliminated. FIG. 12 omits respective portions of the coil 111 and the return path section 140 that are located on the trailing side relative to the main pole 25. In FIG. 12, the portion of the coil 111 located on the trailing side relative to the main pole 25 is shown in a chain double-dashed line.

[0141] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. In the magnetic head according to the present embodiment, the write shield 120 includes a portion that is located farther from the main pole 25 in the track width direction than are the one or more interfaces B1 between the write shield 120 and the return path section 140. In the present embodiment, in particular, the first shield portion 121 includes a portion that is located farther from the main pole 25 in the track width direction than is one of the interfaces B1, i.e., the interface between the write shield 120 and the first yoke portion 141. Further, the second shield portion 122 includes a portion that is located farther from the main pole 25 in the track width direction than is the other one of the interfaces B1, i.e., the interface between the write shield 120 and the second yoke portion 142. The distance between the distal ends of the first shield portion 121 and the second shield portion 122 is greater than the distance between the distal ends of the first yoke portion 141 and the second yoke portion 142.

[0142] Further, in the present embodiment, the third shield portion 123 includes a portion that is located farther from the main pole 25 in the track width direction than are the one or more interfaces B1 between the write shield 120 and the return path section 140. The width of the third shield portion 123 in the track width direction is equal to the distance between the distal ends of the first shield portion 121 and the second shield portion 122, for example.

[0143] Further, in the present embodiment, the fourth portion 124 includes a portion that is located farther from the main pole 25 in the track width direction than are the one or more interfaces B1 between the write shield 120 and the return path section 140. The width of the fourth shield portion 124 in the track width direction is equal to the distance between the distal ends of the first shield portion 121 and the second shield portion 122, for example.

[0144] According to the present embodiment, when compared with the first embodiment, a greater amount of magnetic flux can be captured into the write shield 120 from the end face of the write shield 120 located in the medium facing surface 40. The present embodiment thus makes it possible to prevent unwanted erasure more effectively.

[0145] In the example shown in FIG. 11, all of the first to fourth shield portions 121, 122, 123 and 124 include a portion that is located farther from the main pole 25 in the track width direction than are the one or more interfaces B1. However, in the present embodiment, not all of the first to fourth shield portions 121, 122, 123 and 124 need to include a portion that is located farther from the main pole 25 in the track width direction than are the one or more interfaces B1.

[0146] The remainder of configuration, function and effects of the present embodiment are similar to those of the first embodiment.

[0147] A third embodiment of the present invention will now be described with reference to FIG. 13 to FIG. 17. FIG. 13 is a perspective view showing the main part of the magnetic head. FIG. 14 is a perspective view showing the main part shown in FIG. 13 with some portions eliminated. FIG. 15 is a plan view showing the main part shown in FIG. 13 with some other portions eliminated. FIG. 16 is a cross-sectional view showing the configuration of the magnetic head. FIG. 17 is a cross-sectional view showing a cross section taken at the position indicated by line 17-17 of FIG. 16.

[0148] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. The magnetic head according to the present embodiment has a coil 114 in place of the coil 111 of the first embodiment. In FIG. 13 and FIG. 14 the boundaries between the coil 114 and the leads 112 and 113 are shown by dotted lines. FIG. 14 omits the write shield 120. FIG. 15 omits respective portions of the coil 114 and the return path section 140 that are located on the trailing side relative to the main pole 25. In FIG. 15, the portion of the coil 114 located on the trailing side relative to the main pole 25 is shown in a chain double-dashed line.

[0149] As shown in FIG. 14, of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40, the coil 114 particularly surrounds a portion located on the rear side in the direction of travel of the recording medium (the Z direction) and portions located on opposite sides in the track width direction (the X direction). Thus, the coil 114 does not wrap one turn around the entire outer periphery of the main pole 25. The coil 114 thus passes through the first and second spaces S1 and S2 so as to surround at least part of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40. In the present embodiment, the leads 112 and 113 are located on the front side in the direction of travel of the recording medium relative to the main pole 25 and drawn from opposite ends of the coil 114 in opposite directions along the track width.

[0150] Further, the magnetic head according to the present embodiment has conductive layers 15, 29 and 39 made of a conductive material, in place of the conductive layers 13, 14 and 28 of the first embodiment. The coil 114 is composed of portions of the conductive layers 29 and 30, and the conductive layers 15, 20 and 21. The leads 112 and 113 are composed of the remaining portions of the conductive layers 29 and 30.

[0151] As shown in FIG. 16 and FIG. 17, the conductive layer 15 is shaped to be elongated in the X direction and is disposed on the insulating layer 73. The insulating layer 17 is disposed around the conductive layer 15. In the present embodiment, the insulating layer 18 lies on the conductive layer 15 and the insulating layer 17. The insulating layer 18 has a third opening and a fourth opening in place of the first and second openings of the first embodiment. The third opening exposes a portion of the top surface of the conductive layer 15 adjacent to one end thereof in the longitudinal direction. The fourth opening exposes a portion of the top surface of the conductive layer 15 adjacent to the other end thereof in the longitudinal direction. The conductive layer 20 lies on the conductive layer 15 at the position of the third opening of the insulating layer 18. The conductive layer 21 lies on the conductive layer 15 at the position of the fourth opening of the insulating layer 18.

[0152] As shown in FIG. 17, the conductive layer 29 lies on the conductive layer 20 and the nonmagnetic layer 26. The conductive layer 30 lies on the conductive layer 21 and the nonmagnetic layer 26. The nonmagnetic layer 26 is interposed between the second portion 19B of the magnetic layer 19 and each of the conductive layers 29 and 30. The insulating layer 32 is disposed around the conductive layers 29 and 30.

[0153] In the present embodiment, neither of the portion 141B of the first yoke portion 141 and the portion 142B of the second yoke portion 142 is connected to the third shield portion 123. The second portion 27B of the magnetic layer 27 is shaped to be elongated in the X direction. The second portion 27B is not connected to the first portion 27A of the magnetic layer 27, and is disposed such that the conductive layers 29 and 30 are interposed between the first portion 27A and the second portion 27B.

[0154] The shapes of the first to fourth shield portions 121, 122, 123 and 124 of the present embodiment may be the same as those of the second embodiment. The remainder of configuration, function and effects of the present embodiment are similar to those of the first or second embodiment.

[0155] A fourth embodiment of the present invention will now be described with reference to FIG. 18 to FIG. 23. FIG. 18 is a perspective view showing the main part of the magnetic head. FIG. 19 is a perspective view showing the main part shown in FIG. 18 with some portions eliminated. FIG. 20 is a plan view showing the main part shown in FIG. 18 with some other portions eliminated. FIG. 21 is a cross-sectional view showing the configuration of the magnetic head. FIG. 22 is a cross-sectional view showing a cross section taken at the position indicated by line 22-22 of FIG. 21. FIG. 23 is a cross-sectional view showing a cross section taken at the position indicated by line 23-23 of FIG. 21.

[0156] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. The magnetic head according to the present embodiment has a coil 115 in place of the coil 111 of the first embodiment. In FIG. 18 and FIG. 19 the boundaries between the coil 115 and the leads 112 and 113 are shown by dotted lines. FIG. 19 omits the write shield 120 and the second yoke portion 142 of the return path section 140. FIG. 20 omits respective portions of the coil 115 and the return path section 140 that are located on the trailing side relative to the main pole 25. In FIG. 20, the portion of the coil 115 located on the trailing side relative to the main pole 25 is shown in a chain double-dashed line.

[0157] As shown in FIG. 19, the coil 115 passes through the first and second spaces S1 and S2 so as to surround the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40, and wraps approximately two turns around the entire outer periphery of the main pole 25. In the present embodiment, the leads 112 and 113 are located on the rear side in the direction of travel of the recording medium relative to the main pole 25 and drawn from opposite ends of the coil 115 in opposite directions along the track width.

[0158] In the present embodiment, the yoke length YL, i.e., the distance from the medium facing surface 40 to one of edges of the one or more interfaces B2 between the main pole 25 and the return path section 140 closest to the medium facing surface 40 is greater than that in the first embodiment. The yoke length YL of the present embodiment falls within the range of 1.5 to 4.5 μm, for example.

[0159] Further, the magnetic head according to the present embodiment has conductive layers 16, 22, 23 and 31 made of a conductive material, in addition to the conductive layers 13, 14, 20, 21 and 28. The coil 115 is composed of portions of the conductive layers 13 and 14, and the conductive layers 16, 20 to 23, 28 and 31. The leads 112 and 113 are composed of the remaining portions of the conductive layers 13 and 14.

[0160] As shown in FIG. 22 and FIG. 23, the conductive layers 22 and 23 are located farther from the medium facing surface 40 than are the conductive layers 20 and 21. The conductive layers 20 to 23 are disposed in the space defined by the first portion 19A and the second portion 19B of the magnetic layer 19. The nonmagnetic layer 24 is interposed between the second portion 19B and each of the conductive layers 22 and 23. The conductive layers 22 and 23 are located on opposite sides of the main pole 25 in the track width direction (the X direction) and are each separated from the main pole 25. The top surfaces of the magnetic layer 19, the conductive layers 20 to 23, the main pole 25 and the nonmagnetic layer 24 are even with each other.

[0161] In the present embodiment, as shown in FIG. 23, the conductive layer 14 is located farther from the medium facing surface 40 as compared with the first embodiment. The conductive layer 16 is shaped to be long and narrow, and lies on the insulating layer 73. The conductive layer 16 includes a first portion 16A (see FIG. 23) that is located farther from the medium facing surface 40 than is the conductive layer 13, a second portion 16B (see FIG. 22) that is located closer to the medium facing surface 40 than is the conductive layer 14, and a third portion 16C coupling the first portion 16A and the second portion 16B to each other. In FIG. 22 and FIG. 23 the boundaries between these portions are shown by broken lines. The third portion 16C passes between the conductive layer 13 and the conductive layer 14. The insulating layer 17 is disposed around the conductive layer 16.

[0162] In the present embodiment, the insulating layer 18 lies on the conductive layers 13, 14 and 16 and the insulating layer 17. The insulating layer 18 has the first opening for exposing the top surface of the conductive layer 13 and the second opening for exposing the top surface of the conductive layer 14. Additionally, the insulating layer 18 has a fifth opening (see FIG. 23) for exposing a portion of the top surface of the first portion 16A of the conductive layer 16 adjacent to an edge thereof opposite from the third portion 16C, and a sixth opening (see FIG. 22) for exposing a portion of the top surface of the second portion 16B of the conductive layer 16 adjacent to an edge thereof opposite from the third portion 16C. The conductive layer 20 lies on the conductive layer 13 at the position of the first opening of the insulating layer 18. The conductive layer 21 lies on the second portion 16B of the conductive layer 16 at the position of the sixth opening of the insulating layer 18. The conductive layer 22 lies on the first portion 16A of the conductive layer 16 at the position of the fifth opening of the insulating layer 18. The conductive layer 23 lies on the conductive layer 14 at the position of the second opening of the insulating layer 18.

[0163] As shown in FIG. 21 and FIG. 23, the conductive layer 31 is located farther from the medium facing surface 40 than is the conductive layer 28, and lies on the nonmagnetic layer 26 and the conductive layers 22 and 23. The conductive layer 28 is shaped to be elongated in the X direction. A portion of the conductive layer 28 adjacent to its one end in the longitudinal direction is in contact with the conductive layer 22, and a portion of the conductive layer 28 adjacent to its other end in the longitudinal direction is in contact with the conductive layer 23. The nonmagnetic layer 26 is interposed between the conductive layer 31 and the main pole 25. The nonmagnetic layer 24, the insulating layer 32 and the protective layer 36 are disposed around the conductive layer 31. The conductive layers 28 and 31 are disposed in the space defined by the first portion 27A and the second portion 27B of the magnetic layer 27.

[0164] In the present embodiment, the number of turns of the coil 115 is approximately two, being greater than the number of turns of the coil 111 of the first embodiment. The present embodiment thus makes it possible to increase the magnetomotive force produced by the coil 115 to allow the main pole 25 to produce a write magnetic field of greater magnitude.

[0165] The shapes of the first to fourth shield portions 121, 122, 123 and 124 of the present embodiment may be the same as those of the second embodiment. The remainder of configuration, function and effects of the present embodiment are similar to those of the first or second embodiment.

[0166] A fifth embodiment of the present invention will now be described with reference to FIG. 24 to FIG. 26. FIG. 24 is a perspective view showing the main part of the magnetic head. FIG. 25 is a cross-sectional view showing the configuration of the magnetic head. FIG. 26 is a front view showing the medium facing surface of the magnetic head.

[0167] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes a third yoke portion 143 in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. The third yoke portion 143 is located on the front side in the direction of travel of the recording medium relative to the main pole 25. In FIG. 24 the boundary between the second yoke portion 142 and the third yoke portion 143 is shown by a dotted line.

[0168] As shown in FIG. 24 and FIG. 25, the third yoke portion 143 is connected to the third shield portion 123 so that a third space S3 is defined by the main pole 25, the gap part 130, the third shield portion 123 of the write shield 120, and the third yoke portion 143. In the present embodiment, the third yoke portion 143 is also connected to the portion 141B of the first yoke portion 141 and the portion 142B of the second yoke portion 142 shown in FIG. 1 and FIG. 2. The first coupling portion 145 couples the portion 141B of the first yoke portion 141, the portion 142B of the second yoke portion 142, and the third yoke portion 143 to each other. The coil 111 passes through the third space S3 in addition to the first and second spaces S1 and S2 (see FIG. 3).

[0169] Further, the magnetic head according to the present embodiment has an insulating layer 33 lying on the conductive layer 28 and the insulating layer 32, a magnetic layer 34 made of a magnetic material and lying on the magnetic layer 27 and the insulating layer 33, and an insulating layer 35 lying on the insulating layer 33 and surrounding the magnetic layer 34. The magnetic layer 34 forms the third yoke portion 143. The top surfaces of the magnetic layer 34 and the insulating layer 35 are even with each other. The protective layer 36 lies on the magnetic layer 34 and the insulating layer 35. The insulating layers 33 and 35 are made of alumina, for example.

[0170] According to the present embodiment, the inclusion of the third yoke portion 143 in the return path section 140 provides higher utilization efficiency of the magnetic field produced by the coil 111 when compared with the first embodiment. This effect will be described later in more detail with reference to the results of simulations.

[0171] The shapes of the first to fourth shield portions 121, 122, 123 and 124 of the present embodiment may be the same as those of the second embodiment. The remainder of configuration, function and effects of the present embodiment are similar to those of the first or second embodiment.

[0172] A sixth embodiment of the present invention will now be described with reference to FIG. 27 and FIG. 28. FIG. 27 is a perspective view showing the main part of the magnetic head. FIG. 28 is a cross-sectional view showing the configuration of the magnetic head.

[0173] The magnetic head according to the present embodiment differs from the magnetic head according to the third embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the third yoke portion 143 described in the fifth embodiment section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. In FIG. 27 the boundary between the second yoke portion 142 and the third yoke portion 143 is shown by a dotted line.

[0174] Further, the magnetic head according to the present embodiment has the insulating layers 33 and 35 and the magnetic layer 34 described in the fifth embodiment section. In the present embodiment, the insulating layer 33 lies on the conductive layers 29 and 30 (see FIG. 17) and the insulating layer 32, and is interposed between the magnetic layer 34 and each of the conductive layers 29 and 30.

[0175] The remainder of configuration, function and effects of the present embodiment are similar to those of the third or fifth embodiment.

[0176] A seventh embodiment of the present invention will now be described with reference to FIG. 29 and FIG. 30. FIG. 29 is a perspective view showing the main part of the magnetic head. FIG. 30 is a cross-sectional view showing the configuration of the magnetic head.

[0177] The magnetic head according to the present embodiment differs from the magnetic head according to the fourth embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the third yoke portion 143 described in the fifth embodiment section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. In FIG. 29 the boundary between the second yoke portion 142 and the third yoke portion 143 is shown by a dotted line. The coil 115 passes through the third space S3 in addition to the first and second spaces S1 and S2 (see FIG. 20).

[0178] Further, the magnetic head according to the present embodiment has the insulating layers 33 and 35 and the magnetic layer 34 described in the fifth embodiment section. In the present embodiment, the insulating layer 33 lies on the conductive layers 28 and 31 and the insulating layer 32.

[0179] The remainder of configuration, function and effects of the present embodiment are similar to those of the fourth or fifth embodiment.

[0180] An eighth embodiment of the present invention will now be described with reference to FIG. 31 to FIG. 33. FIG. 31 is a perspective view showing the main part of the magnetic head. FIG. 32 is a cross-sectional view showing the configuration of the magnetic head. FIG. 33 is a front view showing the medium facing surface of the magnetic head.

[0181] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes a fourth yoke portion 144 in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. The fourth yoke portion 144 is located on the rear side in the direction of travel of the recording medium relative to the main pole 25.

[0182] As shown in FIG. 31 and FIG. 32, the fourth yoke portion 144 is connected to the fourth shield portion 124 so that a fourth space S4 is defined by the main pole 25, the gap part 130, the fourth shield portion 124 of the write shield 120, and the fourth yoke portion 144 of the return path section 140. In the present embodiment, the fourth yoke portion 144 is also connected to the portion 141C of the first yoke portion 141 and the portion 142C of the second yoke portion 142 shown in FIG. 2. The second coupling portion 146 couples the portion 141C of the first yoke portion 141, the portion 142C of the second yoke portion 142, and the fourth yoke portion 144 to each other.

[0183] Further, as shown in FIG. 31, the portion 142C of the second yoke portion 142 of the present embodiment is greater in maximum dimension in the Z direction when compared with the example of the first embodiment shown in FIG. 1 and FIG. 2. Although not illustrated, the portion 141C of the first yoke portion 141 of the present embodiment is greater in maximum dimension in the Z direction when compared with the example of the first embodiment shown in FIG. 2, as with the portion 142C of the second yoke portion 142. Further, as shown in FIG. 31 and FIG. 32, the fourth shield portion 124 of the present embodiment is greater in dimension in the Z direction when compared with the example of the first embodiment shown in FIG. 1 and FIG. 4. As shown in FIG. 32, the second coupling portion 146 of the present embodiment is also greater in dimension in the Z direction when compared with the example of the first embodiment shown in FIG. 4.

[0184] The magnetic head according to the present embodiment has a magnetic layer 9 made of a magnetic material and lying on the insulating layer 73 in the vicinity of the medium facing surface 40, and an insulating layer 10 lying on the insulating layer 73 and surrounding the magnetic layer 9. The magnetic layer 9 forms the fourth yoke portion 144. The insulating layer 10 is made of alumina, for example.

[0185] The magnetic head according to the present embodiment further has a magnetic layer 11 made of a magnetic material and lying on the magnetic layer 9. The magnetic layer 11 includes a first portion 11A located between the medium facing surface 40 and the conductive layers 13 and 14, and a second portion 11B located such that the conductive layers 13 and 14 (see FIG. 6) are interposed between the first portion 11A and the second portion 11B. The first and second portions 11A and 11B are both shaped to be elongated in the X direction.

[0186] The magnetic head according to the present embodiment further has an insulating layer 12. The insulating layer 12 lies on the magnetic layer 9 and the insulating layer 10, surrounds the magnetic layer 11 and is interposed between the magnetic layer 9 and each of the conductive layers 13 and 14. In the present embodiment, the insulating layer 17 lies on the insulating layer 12 and surrounds the magnetic layer 11 and the conductive layers 13 and 14. The insulating layer 12 is made of alumina, for example.

[0187] In the present embodiment, the insulating layer 18 has a seventh opening and an eighth opening in addition to the first and second openings described in the first embodiment section. The seventh opening exposes the top surface of the first portion 11A of the magnetic layer 11 at a position near the medium facing surface 40. The eighth opening exposes the top surface of the second portion 11B of the magnetic layer 11 at a position farther from the medium facing surface 40 than the positions of the conductive layers 13 and 14. The first portion 19A of the magnetic layer 19 lies on the first portion 11A of the magnetic layer 11 at the position of the seventh opening of the insulating layer 18. The second portion 19B of the magnetic layer 19 lies on the second portion 11B of the magnetic layer 11 and the insulating layer 18, and is in contact with the second portion 11B at the position of the eighth opening of the insulating layer 18.

[0188] The fourth shield portion 124 is composed of the first portion 11A and a part of the first portion 19A. The portion 141C (see FIG. 2) of the first yoke portion 141 is composed of a part of each of the second portions 11B and 19B. The portion 142C of the second yoke portion 142 is composed of another part of each of the second portions 11B and 19B. The second coupling portion 146 is composed of the remaining part of each of the second portions 11B and 19B.

[0189] According to the present embodiment, the inclusion of the fourth yoke portion 144 in the return path section 140 provides higher utilization efficiency of the magnetic field produced by the coil 111 when compared with the first embodiment. This effect will be described later in more detail with reference to the results of simulations.

[0190] The shapes of the first to fourth shield portions 121, 122, 123 and 124 of the present embodiment may be the same as those of the second embodiment. The remainder of configuration, function and effects of the present embodiment are similar to those of the first or second embodiment.

[0191] A ninth embodiment of the present invention will now be described with reference to FIG. 34 and FIG. 35. FIG. 34 is a perspective view showing the main part of the magnetic head. FIG. 35 is a cross-sectional view showing the configuration of the magnetic head.

[0192] The magnetic head according to the present embodiment differs from the magnetic head according to the third embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the fourth yoke portion 144 described in the eighth embodiment section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. In FIG. 34 the boundary between the second yoke portion 142 and the fourth yoke portion 144 is shown by a dotted line. As shown in FIG. 34, the portion 142C of the second yoke portion 142 of the present embodiment is greater in dimension in the Z direction when compared with the example of the third embodiment shown in FIG. 13 and FIG. 14. Further, although not illustrated, the portion 141C of the first yoke portion 141 of the present embodiment is greater in dimension in the Z direction when compared with the example of the third embodiment shown in FIG. 14, as with the portion 142C of the second yoke portion 142.

[0193] The shapes of the fourth shield portion 124 of the write shield 120 and the second coupling portion 146 of the return path section 140 of the present embodiment are the same as those of the eighth embodiment. The coil 114 passes through the fourth space S4 described in the eighth embodiment section, in addition to the first and second spaces S1 and S2 (see FIG. 15).

[0194] Further, the magnetic head according to the present embodiment includes the magnetic layers 9 and 11 and the insulating layers 10 and 12 described in the eighth embodiment section. In the present embodiment, the conductive layer 15 lies on the insulating layer 12. Further, the second portion 11B is connected to portions of the first portion 11A adjacent to opposite ends thereof in the X direction so that a space is defined by the first portion 11A and the second portion 11B of the magnetic layer 11. The conductive layer 15 is disposed in the space.

[0195] Further, in the present embodiment, the insulating layer 18 has a ninth opening in place of the seventh and eighth openings of the eighth embodiment. The ninth opening has the same planar shape (shape in a plan view) as that of the magnetic layer 11, and exposes the entire top surface of the magnetic layer 11. The magnetic layer 19 is in contact with the magnetic layer 11 through the ninth opening of the insulating layer 18.

[0196] The remainder of configuration, function and effects of the present embodiment are similar to those of the third or eighth embodiment.

[0197] A tenth embodiment of the present invention will now be described with reference to FIG. 36 and FIG. 37. FIG. 36 is a perspective view showing the main part of the magnetic head. FIG. 37 is a cross-sectional view showing the configuration of the magnetic head.

[0198] The magnetic head according to the present embodiment differs from the magnetic head according to the fourth embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the fourth yoke portion 144 described in the eighth embodiment section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. In FIG. 36 the boundary between the second yoke portion 142 and the fourth yoke portion 144 is shown by a dotted line. As shown in FIG. 36, the portion 142C of the second yoke portion 142 of the present embodiment is greater in maximum dimension in the Z direction when compared with the example of the fourth embodiment shown in FIG. 18. Further, although not illustrated, the portion 141C of the first yoke portion 141 of the present embodiment is greater in maximum dimension in the Z direction when compared with the example of the fourth embodiment shown in FIG. 19, as with the portion 142C of the second yoke portion 142.

[0199] The shapes of the fourth shield portion 124 of the write shield 120 and the second coupling portion 146 of the return path section 140 of the present embodiment are the same as those of the eighth embodiment. The coil 115 passes through the fourth space S4 described in the eighth embodiment section, in addition to the first and second spaces S1 and S2 (see FIG. 20).

[0200] Further, the magnetic head according to the present embodiment includes the magnetic layers 9 and 11 and the insulating layers 10 and 12 described in the eighth embodiment section. In the present embodiment, the conductive layers 13 and 14 (see FIG. 22 and FIG. 23) and the conductive layer 16 are located on the insulating layer 12. Further, the magnetic layer 11 has a cavity for accommodating the conductive layer 16. The cavity is surrounded by the first portion 11A and the second portion 11B of the magnetic layer 11. The cavity also accommodates part of each of the conductive layers 13 and 14. The second portion 11B has two notches for drawing the conductive layers 13 and 14 from the cavity of the magnetic layer 11 to outside the magnetic layer 11.

[0201] The remainder of configuration, function and effects of the present embodiment are similar to those of the fourth or eighth embodiment.

[0202] An eleventh embodiment of the present invention will now be described with reference to FIG. 38 to FIG. 40. FIG. 38 is a perspective view showing the main part of the magnetic head. FIG. 39 is a cross-sectional view showing the configuration of the magnetic head. FIG. 40 is a front view showing the medium facing surface of the magnetic head.

[0203] The magnetic head according to the present embodiment differs from the magnetic head according to the first embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the third yoke portion 143 described in the fifth embodiment section and the fourth yoke portion 144 described in the eighth embodiment section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. The fourth shield portion 124 of the write shield 120, and the portion 141C of the first yoke portion 141, the portion 142C of the second yoke portion 142 and the second coupling portion 146 of the return path section 140 of the present embodiment are the same in shape as those of the eighth embodiment.

[0204] Further, the magnetic head according to the present embodiment has the insulating layers 33 and 35 and the magnetic layer 34 described in the fifth embodiment section and the magnetic layers 9 and 11 and the insulating layers 10 and 12 described in the eighth embodiment section.

[0205] The remainder of configuration, function and effects of the present embodiment are similar to those of the first, fifth or eighth embodiment.

[0206] A modification example of the present embodiment will now be described with reference to FIG. 41. FIG. 41 is a perspective view showing the main part of the modification example of the magnetic head according to the present embodiment. The modification example does not have the portion 142C of the second yoke portion 142 shown in FIG. 38. Further, although not illustrated, the modification example does not have the portion 141C (see FIG. 2) of the first yoke portion 141. The remainder of configuration of the modification example is the same as that of the magnetic head according to the present embodiment shown in FIG. 38 to FIG. 40. In the modification example, the second coupling portion 146 (see FIG. 39) couples the fourth yoke portion 144 and the main pole 25 to each other.

[0207] A twelfth embodiment of the present invention will now be described with reference to FIG. 42 and FIG. 43. FIG. 42 is a perspective view showing the main part of the magnetic head. FIG. 43 is a cross-sectional view showing the configuration of the magnetic head.

[0208] The magnetic head according to the present embodiment differs from the magnetic head according to the third embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the third yoke portion 143 described in the sixth embodiment (fifth embodiment) section and the fourth yoke portion 144 described in the ninth embodiment (eighth embodiment) section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. The fourth shield portion 124 of the write shield 120, and the portion 141C of the first yoke portion 141, the portion 142C of the second yoke portion 142 and the second coupling portion 146 of the return path section 140 of the present embodiment are the same in shape as those of the ninth embodiment (eighth embodiment).

[0209] Further, the magnetic head according to the present embodiment has the insulating layers 33 and 35 and the magnetic layer 34 described in the sixth embodiment (fifth embodiment) section and the magnetic layers 9 and 11 and the insulating layers 10 and 12 described in the ninth embodiment (eighth embodiment) section.

[0210] The remainder of configuration, function and effects of the present embodiment are similar to those of the third, sixth or ninth embodiment.

[0211] A thirteenth embodiment of the present invention will now be described with reference to FIG. 44 and FIG. 45. FIG. 44 is a perspective view showing the main part of the magnetic head. FIG. 45 is a cross-sectional view showing the configuration of the magnetic head.

[0212] The magnetic head according to the present embodiment differs from the magnetic head according to the fourth embodiment in the following ways. In the magnetic head according to the present embodiment, the return path section 140 includes the third yoke portion 143 described in the seventh embodiment (fifth embodiment) section and the fourth yoke portion 144 described in the tenth embodiment (eighth embodiment) section, in addition to the first and second yoke portions 141 and 142 and the first and second coupling portions 145 and 146. The fourth shield portion 124 of the write shield 120, and the portion 141C of the first yoke portion 141, the portion 142C of the second yoke portion 142 and the second coupling portion 146 of the return path section 140 of the present embodiment are the same in shape as those of the tenth embodiment (eighth embodiment). The coil 115 passes through the third space S3 described in the seventh embodiment (fifth embodiment) section and the fourth space S4 described in the tenth embodiment (eighth embodiment) section, in addition to the first and second spaces S1 and S2 (see FIG. 20).

[0213] Further, the magnetic head according to the present embodiment has the insulating layers 33 and 35 and the magnetic layer 34 described in the seventh embodiment (fifth embodiment) section and the magnetic layers 9 and 11 and the insulating layers 10 and 12 described in the tenth embodiment (eighth embodiment) section.

[0214] The remainder of configuration, function and effects of the present embodiment are similar to those of the fourth, seventh or tenth embodiment.

[0215] A modification example of the present embodiment will now be described with reference to FIG. 46. FIG. 46 is a perspective view showing the main part of the modification example of the magnetic head according to the present embodiment. The modification example does not have the portion 142C of the second yoke portion 142 shown in FIG. 44. Further, although not illustrated, the modification example does not have the portion 141C (see FIG. 19) of the first yoke portion 141. The remainder of configuration of the modification example is the same as that of the magnetic head according to the present embodiment shown in FIG. 44 and FIG. 45. In the modification example, the second coupling portion 146 (see FIG. 45) couples the fourth yoke portion 144 and the main pole 25 to each other.

[Simulations]

[0216] The effects of the foregoing embodiments of the present invention will now be described in more detail with reference to the results of first and second simulations. The first simulation will be described first. The first simulation used models of magnetic heads of first to third practical examples and models of magnetic heads of third and fourth comparative examples described below. The magnetic heads of the first to third practical examples each correspond to the magnetic head of the present invention.

[0217] The magnetic head of the first practical example is configured so that the return path section 140 includes the first and second yoke portions 141 and 142 and does not include the third and fourth yoke portions 143 and 144, like the first to fourth embodiments.

[0218] The magnetic head of the second practical example is configured so that the return path section 140 includes the first to third yoke portions 141 to 143 and does not include the fourth yoke portion 144, like the fifth to seventh embodiments.

[0219] The magnetic head of the third practical example is configured so that the return path section 140 includes the first to fourth yoke portions 141 to 144, like the eleventh to thirteenth embodiments.

[0220] Each of the magnetic heads of the first to third practical examples has a coil that passes through the first and second spaces S1 and S2 so as to surround at least part of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40.

[0221] The magnetic head of the third comparative example is the same as the magnetic head of the first comparative example described in the first embodiment section. The magnetic head of the fourth comparative example is formed by providing the magnetic head of the third comparative example with a coil wound around the main pole 25 in place of the coil having the first winding portion wound around the first coupling part and the second winding portion wound around the second coupling part.

[0222] In the first simulation, the coils of the aforementioned models were given the same number of turns. Then, the effective write field H_eff was determined for each model. The effective write field is a write magnetic field from the main pole 25 that effectively acts on the magnetic recording layer of a recording medium in order to form a record bit by inverting the magnetization of the magnetic recording layer. The effective write field H_eff is expressed by the following equation using a component H_y of the write magnetic field in a direction perpendicular to the magnetic recording layer (the Y direction), a component H_T of the write magnetic field in the track width direction (the X direction), and a component H_L of the write magnetic field in the direction in which tracks extend (the Z direction).
H_eff={(H_y²+H_T²)^1/3+H_L^2/3}^3/2

[0223] The results of the first simulation will now be described with reference to FIG. 47. FIG. 47 is a characteristic diagram showing the effective write field H_eff determined by the first simulation. In FIG. 47, the horizontal axis represents position on the medium facing surface 40 in the track width direction (the X direction), while the vertical axis represents the effective write field H_eff. On the horizontal axis of FIG. 47, the center position of the end face of the main pole 25 in the track width direction is taken as 0 μm for each model. H_eff is measured in Oe (1 Oe=79.6 A/m). Further, in FIG. 47, the solid line represents the average value of the effective write fields H_eff of the magnetic head models of the first to third practical examples; the dot-and-dash line represents the effective write field H_eff of the magnetic head model of the third comparative example; and the dotted line represents the effective write field H_eff of the magnetic head model of the fourth comparative example. Because the magnetic head models of the first to third practical examples showed effective write fields H_eff of almost the same value, FIG. 47 shows the average value of the effective write fields H_eff of these models.

[0224] As shown in FIG. 47, the magnetic head models of the first to third practical examples have a lower effective write field H_eff in a wide range away from the center of the end face of the main pole 25 in the track width direction, when compared with the magnetic head model of the third comparative example. Further, the magnetic head models of the first to third practical examples have a lower effective write field H_eff particularly in the vicinity of the position of 0.36 μm on the horizontal axis of FIG. 47 when compared with the magnetic head model of the fourth comparative example. At the position of 0.36 μm on the horizontal axis of FIG. 47, the average effective write field H_eff of the magnetic head models of the first to third practical examples was about 57 Oe, the effective write field H_eff of the magnetic head model of the third comparative example was about 131 Oe, and that of the magnetic head model of the fourth comparative example was about 87 Oe. As can be seen from these results, when compared with the magnetic heads of the third and fourth comparative examples, the magnetic head of the present invention is more capable of reducing the magnitude of a magnetic field directed toward the recording medium from a position away from the end face of the main pole 25 in the track width direction, and thus more capable of preventing unwanted erasure.

[0225] The second simulation will now be described. In the second simulation, the magnetic flux rise time defined as below was determined for each of the models employed for the first simulation. The magnetic flux rise time is the time that elapses from the start of generation of a magnetic flux from the end face of the main pole 25 until the amount of the magnetic flux generated from the end face of the main pole 25 reaches 80% of the maximum value. The magnetic flux rise time is a parameter representative of the high frequency characteristics of a magnetic head, showing that the shorter the time, the higher the rate at which the direction of the magnetic flux generated from the end face of the main pole 25 varies. As the frequency of the write signal is increased in order to provide higher recording density, it is required of the write head unit to provide an improved rate of change in the direction of the magnetic flux generated from the end face of the main pole 25, that is, to shorten the magnetic flux rise time. The other conditions for the second simulation were the same as those for the first simulation.

[0226] The results of the second simulation will now be described with reference to Table 1. Table 1 shows the magnetic flux rise time for each model determined by the second simulation. The magnetic flux rise time is in ps. Table 1 also shows the component H_y of the write magnetic field in a direction perpendicular to the magnetic recording layer (the Y direction), determined for each model by the first simulation. H_y is in Oe.

[0227]

	TABLE 1
	Model	Hy (Oe)	Rise time (ps)
	Third practical example	7284	65.9
	Second practical example	7276	66.1
	First practical example	7275	66.4
	Fourth comparative example	7271	66.8
	Third comparative example	7241	68.0

[0228] As shown in Table 1, for each of the magnetic head models of the first to third practical examples, the component H_y of the write magnetic field is greater and the magnetic flux rise time is shorter, when compared with the magnetic head models of the third and fourth comparative examples. This suggests that the magnetic head models of the first to third practical examples provide higher utilization efficiency of the magnetic field produced by the coil when compared with the magnetic head models of the third and fourth comparative examples.

[0229] The magnetic head model of the second practical example is greater in component H_y of the write magnetic field and shorter in magnetic flux rise time than the magnetic head model of the first practical example. Further, the magnetic head model of the third practical example is greater in component H_y of the write magnetic field and shorter in magnetic flux rise time than the magnetic head model of the second practical example. These results show that in the magnetic head of the present invention, the inclusion of at least one of the third yoke portion 143 and the fourth yoke portion 144, in addition to the first and second yoke portions 141 and 142, in the return path section 140 allows further enhancement of the utilization efficiency of the magnetic field produced by the coil.

[0230] The benefit of being able to enhance the utilization efficiency of the magnetic field produced by the coil, provided by the magnetic head of the present invention, becomes more noticeable particularly when the coil has a smaller number of turns. Now, this will be described below. It can be generally said that the less the minimum value of the write current (hereafter referred to as the minimum write current value) required to obtain desired write characteristics, the higher the performance of the write head unit. For the write head unit including the write shield and the return path section, the minimum write current value depends on the volume of the magnetic path formed by the main pole, the write shield and the return path section, and the magnetomotive force of the coil. In general, the volume of the magnetic path formed by the main pole, the write shield and the return path section increases with an increase in the yoke length which is the distance from the medium facing surface to one of edges of the one or more interfaces between the main pole and the return path section that is closest to the medium facing surface. Thus, the minimum write current value can be said to be dependent on the yoke length and the magnetomotive force of the coil. The minimum write current value decreases as the yoke length decreases and as the magnetomotive force of the coil increases.

[0231] On the other hand, as described above, as the frequency of the write signal is increased in order to provide higher recording density, it is required of the write head unit to provide an improved rate of change in the direction of the magnetic flux generated from the end face of the main pole. To meet this requirement, the write head unit including the write shield and the return path section desirably has a shorter yoke length. In general, however, shortening the yoke length requires that the number of turns of the coil be reduced. Thus, shortening the yoke length should result in a reduction of the magnetomotive force of the coil.

[0232] Typical magnetic heads that have been mass-produced often have a coil of three or four turns. On the other hand, the yoke length is about 8.5 μm for a coil of four turns, and about 6.5 μm for a coil of three turns. From this, it is conceivable that the yoke length will be about 4.5 μm for a coil of two turns, and about 2.5 μm for a coil of one turn.

[0233] Table 2 shows the relationship between the yoke length, the number of turns of the coil, and the yoke length per turn of the coil. The yoke length per turn of the coil is the yoke length divided by the number of turns of the coil.

[0234]

TABLE 2
Yoke length	Number of	Yoke length per turn of coil
(μm)	turns of coil	(μm/number of turns)
8.5	4	2.13
6.5	3	2.17
4.5	2	2.25
2.5	1	2.50

[0235] Table 2 shows that the smaller the number of turns of the coil, the greater the yoke length per turn of the coil becomes. This means that as the number of turns of the coil is reduced, the volume of the magnetic path that has to be driven by one turn of the coil increases when a current of the same value flows through the coil. Accordingly, the minimum write current value may increase as the number of turns of the coil is reduced.

[0236] Thus, in order to inhibit an increase in the minimum write current value even when the number of turns of the coil is as small as one or two, it is necessary to reduce the yoke length or improve the structure of the return path section so as to utilize more efficiently the magnetic field produced by the coil. Reducing the yoke length would require that the magnetic head be manufactured with higher precision, thus placing additional burden on the manufacturing process of the magnetic head. It is thus desirable to inhibit an increase in the minimum write current value by improving the structure of the return path section.

[0237] According to the magnetic head of the present invention, the return path section 140 includes the first and second yoke portions 141 and 142, and the coil 111, 114 or 115 passes through the first and second spaces S1 and S2 so as to surround at least part of the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40. This allows the utilization efficiency of the magnetic field produced by the coil to be higher than that provided by the magnetic heads of the third and fourth comparative examples. Furthermore, structurally, the return path section 140 of the magnetic head of the present invention can include at least one of the third yoke portion 143 and the fourth yoke portion 144. The inclusion of at least one of the third yoke portion 143 and the fourth yoke portion 144 in the return path section 140 allows further enhancement of the utilization efficiency of the magnetic field produced by the coil. In this manner, the magnetic head of the present invention makes it possible to inhibit an increase in the minimum write current value. This benefit becomes more noticeable particularly when the number of turns of the coil is as small as one or two.

[0238] Now, a description will be made as to the effect provided by the particular configuration in which the coil 111 or 114 does not wrap one turn around the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40. First, to reduce the resistance of the conductor made up of the coil and the leads 112 and 113, a cross section of the conductor orthogonal to the direction of current passing through the two leads 112 and 113 connected to opposite ends of the coil is preferably shaped to increase in size immediately after the coil. To that end, in view of space in the magnetic head, the two leads 112 and 113 are preferably drawn from the coil in opposite directions along the track width.

[0239] Where the coil wraps one or more turns around the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40, drawing the two leads 112 and 113 from the coil in opposite directions along the track width would inevitably result in a structure in which two or more portions of the coil lie side by side in the Y direction. In this case, the manufacturing process of the coil is complicated and it is not possible to reduce the yoke length YL.

[0240] In contrast, where the coil does not wrap one turn around the entire outer periphery of the main pole 25 when viewed from the medium facing surface 40, it is possible to draw the two leads 112 and 113 from the coil in opposite directions along the track width without necessitating the structure in which two or more portions of the coil lie side by side in the Y direction. In this case, the manufacturing process of the coil is simplified and a reduction of the yoke length YL is possible.

[0241] The present invention is not limited to the foregoing embodiments, and various modifications may be made thereto. For example, the magnetic head of the present invention may be a thermally-assisted magnetic recording head or a microwave-assisted magnetic recording head provided with a means for applying heat or a microwave magnetic field to a recording medium.

[0242] It is apparent that the present invention can be carried out in various forms and modifications in the light of the foregoing descriptions. Accordingly, within the scope of the following claims and equivalents thereof, the present invention can be carried out in forms other than the foregoing most preferred embodiments.