Exchange coupling field in top, bottom, and dual-type IrMn spin valves coupled to CoFe

Abstract

A comparative study of Co75Fe25/Ir22Mn78 exchange biased top, bottom, and dual-type spin valves is presented. IrMn pinned spin valves were prepared by do magnetron sputtering onto thermally oxidized Si (111) substrates at a room temperature under a magnetic field of about 100 Oe. For as-deposited top -type spin valves, the magnetoresistance (MR) ratio and exchange coupling field (H-ex) were 5.6% and 430 Oe, respectively. For bottom IrMn based spin valves, the H-ex values are much higher (H-ex = 1180 Oe) while MR ratio (3.6%) is reduced with respect to the top spin valves. The blocking temperatures (T-B) of the top and bottom SV were 250 degreesC and 270 degreesC, respectively. The results concerning magnetic properties together with structural investigations suggest that H-ex is mainly dependent on the quality of fee (111) crystalline texture while MR ratio is sensitive to both crystalline texture and interface roughness. Dual -type spin valves, with the MR ratio of 7.6% and H-ex of 850/510 Oe, showed two exchange loops due to the differences in H-ex between the top and bottom pinning layers.