IMPROVEMENT OF THERMAL-STABILITY AND MAGNETORESISTANCE RECOVERY OF TB25CO75 BIASED SPIN-VALVE HEADS

The thermal stability of TbCo exchange biased spin valve sensors has b een extended to 230 degrees C, by using a Co pinned layer rather than NiFe. Magnetoresistance (MR) remains essentially stable up to annealin g temperatures T-A of 230 degrees C and degrades to 1% at T-A = 240 de grees C. Providing T-A does not exceed 230 degrees C, any loss in the MR signal can be fully recovered by applying a field perpendicular to the film plane, This improved thermal stability allows processing at h igher temperatures. The unidirectional exchange in the TbCo/Co interfa ce becomes uniaxial for T-A > 100 degrees C. Even though the unidirect ional character was not recovered by any field/anneal treatment, uniax ial anisotropy above 120 Oe is maintained for T-A = 260 degrees C. Dev ices were fabricated using a process with a maximum temperature of 180 degrees C. No MR loss is found during process in test structures at w afer level. A prototype 10-mu m-track width spin valve tape head for Q IC applications gave a maximum output of 2.3 mV(pp) at 20 kfci. (C) 19 97 American Institute of Physics.