Magnetic and thermal effects of flying height control heater voltage on tunneling magnetoresistive heads

摘要

The resistance and signal amplitude of tunneling magnetoresistive (TMR) heads were investigated as a function of flying height control (FHC) heater voltage under nonflying condition. The resistance and signal amplitude measured with a quasistatic tester (QST) both during and after FHC heater voltage application are substantially different from the initial values. The change of resistance or amplitude is reversible up to 3.2 V (approx204 deg C). However, there are permanent changes in TMR signal amplitude after voltage applications of 3.4 V (approx225 deg C) and above. An additional test, where QST performances of heads were measured only after FHC voltage applications, was carried out to distinguish between magnetic fields from the FHC heater and from the QST. Still, there are significant changes in resistance and amplitude. Pin layer reversals by the FHC heater current were also observed.