Tailoring the exchange bias effect by in-plane magnetic anisotropy

We report an unusual, non-monotonous dependence of the exchange bias on the thickness of the ferromagnetic layer in a ferromagnet/antiferromagnet bilayer system. We show that in epitaxial CoO/Fe(110) bilayers, the evolution of the Fe magnetic anisotropy, which drives the thickness-induced in-plane spin-reorientation process, controls the interfacial CoO spin directions in the 0-90 degrees range and, consequently, drastically modifies the magnitude of the hysteresis loop shift and its dependence on the thickness of the Fe layer. Our results present a new recipe for tailoring the exchange bias and antiferromagnetic spin structure by utilizing the spin-reorientation process that occurs in a ferromagnetic layer adjacent to an antiferromagnetic layer.