The influence of annealing on the bimodal distribution of blocking temperatures of exchange biased bilayers

Abstract

AbstractThe exchange bias effect at the interface between antiferromagnetic (AFM) and ferromagnetic (FM) layers is of paramount importance in state‐of‐the‐art spintronic devices. However, a complete account of the physics behind exchange bias remains elusive and new effects are constantly unraveled. In particular, a bimodal distribution of blocking temperatures $ (T_{\rm B})$ was recently discovered, associated with the bulk of the AFM layer and interfacial AFM/FM regions with spin‐glass‐like properties. Here we study exchange bias in MnIr (25, 60 Å)/CoFe (50 Å) bilayers annealed at high temperatures (623 K and 673 K). We observe, for all samples and annealing temperatures, the existence of a large exchange bias variation at low temperatures associated with interfacial disorder. Such variation is more significative in the thinnest samples, where it is found to be independent on annealing temperature. On the other hand, in the thickest samples the contribution of the low temperature distribution largely increases with annealing temperature, due to enhanced disorder arising from Mn diffusion. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)