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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 substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of the exchange-coupling field (Hex), magnetoresistance (MR) ratio, and coercivity (Hc) 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%, Hex of 1180 Oe for the pinned layer. The Hex is stabilized after the second annealing cycle, and it is thought that this SV reveals high thermal stability. The Hex maintained its strength of 600 Oe in operation up to 240°C and decreased monotonically to zero at 270°C.
Date of Publication: Sep 2002