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 ℃ and decreased monotonically to zero at 270 ℃.
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