The structure dependence of exchange bias in ferromagnetic/antiferromagnetic bilayers

The structure dependence of exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayers has been investigated in detail by extending Slonczewski's `proximity magnetism' idea. Here three important parameters are discussed for FM/AF bilayers, i.e. interfacial bilinear exchange coupling $J_{1}$, interfacial biquadratic (spin-flop) exchange coupling $J_{2}$ and antiferromagnetic layer thickness $t_{\rm AF}$. The results show that both the occurrence and the variety of the exchange bias strongly depend on the above parameters. More importantly, the small spin-flop exchange coupling may result in an exchange bias without the interfacial bilinear exchange coupling. However, in general, the spin-flop exchange coupling cannot result in the exchange bias. The corresponding critical parameters in which the exchange bias will occur or approach saturation are also presented.