Spin Hall Magnetoresistance in Pt/BiFeO₃ Bilayer

Multiferroic materials are general antiferromagnets with negligibly small net magnetization, which strongly limits their magnetoelectric applications in spintronics. Spin Hall magnetoresistance (SMR) is sensitive to the orientation of the Néel vector, which can be applied for the detection of antiferromagnetic states. Here, we apply SMR on the unique room-temperature antiferromagnetic multiferroic material BiFeO₃ (BFO). The angular dependence of SMR in a bilayer of epitaxial BFO (001) and heavy metal Pt is studied. By rotating the sample under a magnetic field of 80 kOe in the film plane, the resistance shows the maximum when the field is perpendicular to the current while it shows the minimum when the field is along the current. This can be well explained by the SMR in the bilayer of heavy metal/antiferromagnet with the relative orientation between the Néel vector and current direction. In contrast, the angular dependence of the resistance of Pt directly deposited on a SrTiO₃ (001) substrate shows a 90° shift with the magnetic field rotating in the film plane, which originates from the Hanle magnetoresistance of Pt. The obtained spin mixing conductance at the Pt/BFO interface clearly confirms the efficient spin transmission. Our results provide a possible solution for applications of antiferromagnetic multiferroic materials in spintronics.