Influence of strong anisotropy of CoFe layer on the reversal asymmetry and training effect in Ir22Mn78/Co60Fe40 bilayers

Abstract

In this work, we report a study of the influence of large anisotropy of CoFe layer on the reversal asymmetry and training effect in exchange biased IrMn/CoFe bilayers. The existence of a strong single cycle training effect and an accompanying distinct reversal asymmetry at 15 K have been demonstrated using magnetoresistance as a probe. The temperature dependent change in the symmetry (uniaxial to biaxial) of IrMn anisotropy has been proposed as the primary cause of the occurrence of pronounced reversal asymmetry and large training effect below 50 K. In particular, the present findings indicate that the observed differences between IrMn/CoFe and IrMn/NiFe [Fulara et al., Appl. Phys. Lett. 101, 142408 (2012)] systems in their asymmetric behaviour of magnetization reversal and training effect are linked with the interplay between the interfacial spin frustration and the intrinsic ferromagnetic anisotropy.