Bottom pole structure with recessed section

#The invention relates to the general field of magnetic write heads with particular reference to improving track density.

#To enable increases in the recording density achieved by a magnetic head, the coercivity of the recording media must be increased to overcome the demagnetization field of the magnetic transition. However as the track width decreases, so does the head field. When a high-end hard disk drive (HDD) generates a high data transfer rate, in the order of 1 Gbit/s, or more, not only is greater head field strength required, but there also is a need for a faster flux rise time. In order to achieve a large enough overwrite value, even in such high frequency conditions, the write current is boosted, giving its waveform a large overshoot. This often brings about severe excess saturation of the head and, as a result, adjacent track erasures often occur.

#FIG. 1 is a schematic illustration of a conventional planar write head while FIG. 2 shows a closeup of the vicinity of the pole tip region. The design implements a bottom pole 11 (P1), pedestal 12 (P1P) and small throat height region 13 (for flux concentration), which opposes plane top pole 14 (P2)across from write gap 15. These poles are made of soft magnetic materials such as Ni, Co, Fe or their composites. The coil layer is packed onto the P1, and the P2 pole is fabricated on a planar surface to allow good track width control for the P2 tip width definition. The write gap material is a non-magnetic conductor such Cu, Au, Al, Cr, Rh or their composite.

#FIGS. 1 and 2 show two views of a planar write head of the prior art.

#FIG. 3 shows different leakage paths for the flux between P1 and P2.

#FIG. 4 plots the write field (of a prior art device) as a function of distance from the write gap, illustrating how there is a peak in the vicinity of the P1 shoulder.

#We now disclose four embodiments of a novel P1 structure for a planar write head.

#FIG. 5a shows the cross section and FIG. 5b the ABS view of a typical example of the new P1 pole structure. The P1 pedestal's ABS includes a partial indentation, or recess, 51 away from the ABS, the structure being characterized by the dimensions of the various sub-structures that, together, make up the P1 pedestal. The recessed region 51 of the P1 pedestal is filled with a nonmagnetic material.

#The way the new design feature works is explained by the illustration in FIG. 6. The closed arrows denote the flow of flux from the P1 to the P2 pole for a low or medium write current of less than 40 mA. However, for a high write current (larger than 40 mA), the P1 pedestal becomes magnetically saturated in constricted region 45 (P1B), causing excess flux to go through to P2. from the backside of 62 (P1C) as indicated by open white arrow 61. This prevents said excess flux from appearing at the ABS at the P1 shoulder. As shown in FIG. 6, the inner surfaces of elements 45 and 62 are coplanar.