Comparative study of MR head designs with abutted vs. overlaid permanent magnet bias

We have developed Soft-Adjacent-Layer (SAL)-biased MR head products with two types of permanent magnet (PM) domain stabilization schemes, namely, abutted and overlaid. Both types of MR heads are capable of achieving recording density of 500 Mb/in/sup 2/ with linear bit densities ranging from 100-118 kbpi. While transfer curves with a transverse sweeping field showed similar behavior for both PM schemes, the overlaid structure has a large hysteresis in its transfer curve under a longitudinal sweeping field while the abutted junction was hysteresis free. Micromagnetic modeling showed that the hysteresis for the overlaid scheme arises from the varying field response of the MR element in the active region, under the leads and under the PM. Magnetic test shows that the abutted MR head with a PM defined TW had a slower rise in sensitivity and had an effectively narrower magnetic track width. On the other hand, the overlaid MR head with an active region defined by the leads with MR under them has a steeper rise in sensitivity, a broadened magnetic read track and side readings.