Instability of Output Signals and Its Relationship with the Domain Structure in MR Heads

Abstract

Instability is studied for an SAL-biased MR head with abutted permanent magnets. An MR head with insufficient longitudinal bias is simulated by demagnetizing the permanent magnets. The values of the output and the peak asymmetry fluctuate between two states, one with high output and small asymmetry, and the other with low output and highly negative asymmetry. In the low output state, microtrack profile measurements taken while varying the value of the sensing current show the MR layer to be in a buckling domain structure. This causes a hysteresis in the output versus sensing current curves. The buckling domain structure can be changed into a single-domain structure by increasing the sensing current above a certain level. This brings the head back into the high-output state.