The effect of cyclic annealing treatments on magnetoresistance in IrMn‐pinned top and bottom spin valves

Abstract

IrMn-pinned top spin valve (TSV) and bottom spin valve (BSV) films were prepared by DC magnetron sputtering onto thermally oxidized Si (111) substrates at room temperature under a magnetic field of above 100 Oe. The effect of cyclic annealing treatments on magnetoresistive and structural properties in the films was investigated. The exchange coupling field (Hex) of TSV and BSV is stabilized after the second annealing cycle and it is thought that these films reveal high thermal stability. The magnetoresistance (MR) ratio and Hex of TSV were 5.6% and 430 Oe, respectively. For BSV the Hex value (1180 Oe) is much higher while MR ratio (3.6%) is reduced with respect to TSV. The blocking temperatures of the TSV and BSV were 250 °C and 270 °C, respectively. The results concerning magnetic properties together with structural investigations suggest the Hex is mainly dependent on the quality of fcc (111) crystalline texture while MR is sensitive to both crystalline texture and interface roughness. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)