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.