Strain-dependent spin Hall magnetoresistance in the multiferroic antiferromagnet BiFeO3

The spin Hall magnetoresistance (SMR) of antiferromagnetic BiFeO3 thin film surfaces is investigated. SMR consistent with weak ferromagnetic order in films fabricated on (001) SrTiO3 (R′ BFO) and LaAlO3 (T′ BFO) substrates is found, albeit with different temperature dependencies. For T′ BFO, the SMR is enhanced at room temperature, and decays with reduced temperatures. By contrast, R′ BFO shows a monotonic decrease in SMR response with increasing temperature, mirroring the trend of a weak ferromagnet. Density functional theory shows that this intriguing difference originates due to the different octahedral rotation patterns in R′ and T′ BFO and their coupling to the applied magnetic field and spin degrees of freedom.