Spin Hall magnetoresistance in antiferromagnetic α-Fe2O3/Pt bilayers: Modulation from interface magnetic state

In this work, we have prepared an antiferromagnetic insulated α-Fe2O3 film with a large out-of-plane magnetic component and studied the spin Hall magnetoresistance (SMR) in α-Fe2O3/Pt bilayers. Both angular-dependent magnetoresistance and field-dependent magnetoresistance have featured a sign change characteristic with varying temperature, which is ascribed to the competition between a modulated interface magnetic state and an antiferromagnetic bulk state of the α-Fe2O3 film. According to a generalized theoretical model, which takes the effective spin conductance into consideration, the spin transport can be mathematically expressed as the change of field dependent average spin operators with varying temperature. The critical temperature also depends on the α-Fe2O3 film thickness and the magnetic field, which are ascribed to the magnons transport and long-range order of non-collinear spin textures, respectively. Furthermore, we have given a phenomenological form to fit the SMR curves in the critical temperature interval, which further reveals the origin of SMR with complex magnetic structures.