Control of the Interfacial Exchange Coupling Energy in Pt/Co/α-Cr2O3 Films by Inserting a Pt Spacer Layer at the Co/α-Cr2O3 Interface

We investigated the control of the perpendicular exchange bias (PEB) in Pt/Co/alpha-Cr2O3 (0 0 0 1) thin films that exhibit a unique temperature dependence of the PEB. Previously, we demonstrated that the onset of the PEB is explained by the competition between the interface coupling energy and the magnetic anisotropy energy in the alpha-Cr2O3 layer. Based on this finding, in this study, we investigated the influence of a Pt spacer layer at the Co/alpha-Cr2O3 interface to control the interface exchange coupling. By inserting a Pt spacer layer, the unidirectional magnetic anisotropy energy J(K) was reduced because of the weakened exchange coupling between Co and alpha-Cr2O3. The weakened direct exchange coupling caused an increase in the onset temperature of J(K), resulting in a reduction in the alpha-Cr2O3 layer thickness necessary to maintain the PEB up to the Neel temperature. In addition, the change in the interface exchange coupling mechanism between Co and alpha-Cr2O3 is discussed with respect to the temperature dependence of J(K).