Exchange bias in antiferromagnetic-ferromagnetic-antiferromagnetic structures with out-of-plane magnetization

摘要

Exchange bias effects are investigated in antiferromagnetic- (AF_1-) ferromagnetic- (F-) antiferromagnetic (AF_2) structures, where the F consists of a [Pt/Co] multilayer with perpendicular anisotropy and the two AF layers are composed of IrMn. The AF_1 and AF_2 thicknesses are varied so that the two IrMn layers exhibit different blocking temperatures. After field cooling, enhancements of the coercivity H_C and exchange bias field H_E are observed in the AF_1-F-AF_2 structures with respect to the two subsystems with a single AF layer (i.e., AF_1-F and F-AF_2). For all systems, the magnitude and sign of H_E can be subsequently tailored by field cooling processes under fields of different sign while H_C remains constant. The net effect of having two AF-F interfaces is roughly the sum of each individual interface contribution.