Process and structure for a perpendicular writer having an exchange coupling discontinuity

[0001] The invention relates to the general field of vertical magnetic writers with particular reference to the pole erasure problem.

[0002] As magnetic recording is pushed to higher areal densities, perpendicular media may offer the advantage of thermal stability over longitudinal media. Despite the rapid progress of perpendicular recording technology in recent years, there remain a few technical challenges. One of these is the non-zero remanence state that is associated with a single pole writer after the write current has been terminated, often referred as self-pole-erasure (SPE).

[0003] The physical origin of SPE is the strong ferromagnetic exchange coupling of pole tip while in its remanent state, which aligns the magnetization vertically and causes the erasure of data on disk. SPE will be aggravated when the perpendicular media are DC magnetized and the magnetic field generated from said perpendicular media causes the vertical remanent state to be energy-favorable.

[0004] This invention improves pole erasure performance associated with a PMR writer. It provides an alternative solution to the pole erasure problem by changing only the geometry/structure of the main pole, without changing pole materials. The process is compatible with current practice. When combined with future material improvements, even greater reductions of pole erasure can be expected.

[0005] A routine search of the prior art was performed with the following references of interest being found: In U.S. Pat. No. 6,721,131 and in U.S. Patent Application 2002/0131203, Litvinov et al disclose a decoupling layer between high and low magnetic moment portions of a write pole to minimize magnetic remanence. In order to minimize changes to the process for manufacturing their write head they place this decoupling layer in a plane normal to the ABS (air bearing surface), thereby surrendering the possibility of shaping the pole piece so as to concentrate the write flux in the pole tip. The present invention teaches a structure and process whereby the decoupling layer is placed in a plane that is parallel to the ABS.

[0006] It has been an object of at least one embodiment of the present invention to reduce or eliminate self-pole-erasure by a vertical magnetic write head.

[0007] Another object of at least one embodiment of the present invention has been to achieve this with a minimum of modification of the write head structure currently in use.

[0008] Still another object of at least one embodiment of the present invention has been to achieve this without requiring that the materials used to form the write pole be changed.

[0009] A further object of at least one embodiment of the present invention has been to provide a process for manufacturing said improved write head.

[0010] These objects have been achieved by inserting a very thin exchange de-coupling layer into the magnetic circuit of the write pole. This facilitates vortex formation at the pole tip region so the remanent field is significantly reduced, along with pole erasure. Because of the small thickness of this decoupling layer, the increase of magnetic reluctance due to the insertion of the exchange-breaking gap is negligible and the efficiency of writing is not affected.

[0016] In most current PMR writer designs, the main pole is processed from one layer of a continuous thin film. So the exchange coupling is also continuous. By introducing a very thin exchange de-coupling layer, vortex formation is facilitated in the pole tip region and the remanent field is significantly reduced, along with pole erasure. Because of the small thickness of this decoupling layer, the increase of magnetic reluctance due to the exchange-breaking gap is negligible and the efficiency of writing is not affected.

[0017] FIGS. 1a and 1b show plan and cross-sectional views respectively of the invented perpendicular write head. Seen there are yoke portion 11 and pole tip 13 between which has been inserted exchange-breaking layer 12. FIG. 2 shows the simulated perpendicular field in its remanent state for PMR heads with and without a discontinuity in the exchange coupling. When there is broken exchange decoupling, vortex formation is facilitated (curve 22). Without exchange decoupling, however, the magnetization tends to align vertically so the remanent field is significantly larger (curve 21). In the simulation, the distance of the exchange-breaking gap from ABS (air bearing surface) 14 was 0.4 microns. Due to the small gap thickness, the increase of magnetic reluctance resulting from the blocking of the exchange coupling was negligible (less than about 5%) and the writing efficiency was not measurably affected.

[0018] We now disclose the invention in greater detail through a description of a process for its manufacture. This description will also serve to further clarify the structure of the invention. Referring next to FIGS. 3 and 4, the process of the invention begins with the provision of base layer 32 on the top of a completed reader structure (not shown) onto whose surface is deposited layer 31 of a material having high saturation magnetic induction. Layer 32 would typically be of a material such as alumina, while layer 31 could be any alloy of Co, Fe, or Ni, including materials such as CoFe, CoFeNi, with CoFeNi being preferred. Layer 31 is deposited to a thickness between about 0.1 and 2 microns.

[0019] Layer 32 and layer 31 are simultaneously patterned into the shape shown in FIG. 3. As can be seen in FIG. 3, said shape comprise three contiguous regions:

[0020] Region A, the write pole, has a constant width 32, between about 0.05 and 0.3 microns, and length 33 of up to about 0.5 microns, measured from the ABS. Region C, the yoke, has a constant width 34 (that is greater than width 32) of between about 5 and 40 microns, and length 35, between about 5 and 30 microns. Region B connects regions A and C. It has length 36, and a width that varies from that of 32 to that of 34.

[0021] Moving on to FIGS. 5 and 6, trench 61 is formed. It extends downwards from the upper surface to a depth 62, between about 0.1 and 1 microns, that exceeds the thickness of layer 31. Sidewalls 62 of the trench are, preferably, vertical and are generally located within region B at a distance of between about 0.1 and 2 microns from the ABS. This is followed by the deposition of layer 81 of non-magnetic material (such as Ru, Pd, Cu, or Ta that uniformly coats trench 61's sidewalls to a thickness of between about 1 and 200 Angstroms, as illustrated in FIGS. 8 and 9.

[0022] Trench 61 is then over-filled with additional high magnetic saturation material 91, optionally with a different composition from layer 31, following which the surface is planarized until the original upper surface of layer 31 is exposed once more. The completed device now has the appearance illustrated in FIGS. 9 and 10.