Modeling and measurement of hard-magnet biasing strengths on MR-SAL structures

MR sensors using a SAL for transverse biasing, and patterned hard-magnets for longitudinal biasing have been fabricated and tested. The permanent magnet biasing fields of these MR-SAL structures are investigated both theoretically and experimentally. Increasing the external longitudinal offset field along the permanent magnet biasing direction stabilizes the transverse response and reduces the device sensitivity; increasing this field along the opposite direction causes magnetic hysteresis. The threshold offset field at the onset of Barkhausen noise measures the average permanent-magnet longitudinal biasing strength. Good correlations with other test methods and micromagnetic simulations are obtained