INSTABILITY EVALUATION FOR PERMANENT-MAGNET BIASED MAGNETORESISTIVE HEADS

We have used micromagnetic modeling to study instability of permanent magnet biased magnetoresistive heads. A new approach based on the depe ndence of reproducing characteristics on initial magnetization is prop osed to examine the instability of both AMR and spin-valve heads. When the permanent magnet strength is smaller than a critical value, the o utput voltage of an AMR head depends on the initial magnetization, whi ch results in instability. The critical permanent magnet strength grad ually increases as shield-to-shield separation decreases. The critical value for spin-valve heads is smaller than that for AMR heads, becaus e the pinned layer under a large exchange field does not change its ma gnetization at all.