High exchange-coupling field and thermal stability of antiferromagnetic Ir-Mn pinned spin-valve films

IrMn pinned spin-valve (SV) films with stacks of Ta-NiFe-IrMn-CoFe-Cu-CoFe-NiFe-Ta were prepared by dc sputtering onto thermally oxidized Si[111] substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of the exchange-coupling field (H/sub ex/), magnetoresistance (MR) ratio, and coercivity (H/sub c/) were investigated. By optimizing the process of deposition and the post-thermal annealing condition, we obtained the IrMn-based SV films with MR ratio of 3.6%, H/sub ex/ of 1180 Oe for the pinned layer. The H/sub ex/ is stabilized after the second annealing cycle, and it is thought that this SV reveals high thermal stability. The H/sub ex/ maintained its strength of 600 Oe in operation up to 240/spl deg/C and decreased monotonically to zero at 270/spl deg/C.