Thickness dependence of positive exchange bias in ferromagnetic/antiferromagnetic bilayers

For the ferromagnetic (FM)/antiferromagnetic (AFM) bilayers, both negative and positive exchange bias HEHE have been observed for low and high cooling field HCFHCF, respectively. The thickness dependence of HEHE and coercivity HCHC have been investigated for the cases of negative and positive HEHE. It is found that the negative HEHE and the positive one have similar FM thickness dependence that is attributed to the interfacial nature of exchange bias. However, the AFM thickness dependence of positive HEHE is completely contrary to that of the negative one, which clearly demonstrates that the AFM spins play different roles for the cases of positive and negative HEHE. In particular, the AFM thickness of positive HEHE was first highlighted by an AFM spin canting model. These results should be attributed to the interfacial spin configuration after field cooling procedure.

► The AFM spins play different roles for the cases of positive and negative HEHE.
► The tAFtAF dependence of positive HEHE was first highlighted by a spin canting model.
► Our results can be attributed to the interfacial spin configuration after cooling.