Exchange coupling in ferromagnetic/antiferromagnetic/ferromagnetic [Pd/Co]n/NiO/Co trilayers with different [Pd/Co] anisotropy

Abstract Exchange coupling in NiO/Co bilayers and [Pd/Co( t Co )] n /NiO/Co trilayers prepared by magnetron sputtering has been investigated. With decreasing thickness ( t Co ) of the Co layers in [Pd/Co] multilayers (MLs) and increasing number of [Pd/Co] repeats ( n ), the ferromagnetic easy axis of the [Pd/Co] MLs switches from in-plane to out-of-plane direction. Ferromagnetic and non-collinear interlayer couplings between the [Pd/Co] MLs and the Co layer across the antiferromagnetic NiO spacer are found in trilayers. After cooling at in-plane and out-of-plane remanent state, respectively, for t Co =1 nm and n =2, a larger in-plane exchange bias field of 724 Oe is observed which vanishes at temperatures above 90 K which is the same as the in-plane blocking temperature observed in the NiO/Co bilayer. For t Co =0.3 nm and n =7, the in-plane blocking temperature in the trilayer enhances up to 210 K, which strongly depends on orientation and strength of the ferromagnetic [Pd/Co] ML anisotropy axis.