Magnetotransport properties of γ-FeMn thin films grown by high-temperature sputtering

γ-FeMn is a topological antiferromagnet which hosts a noncoplanar spin structure at room temperature, promising for application to antiferromagnetic spintronics. In this work, we have investigated magnetotransport properties of FeMn thin films grown by dc magnetron sputtering on Al2O3 (0001) substrates. γ-phase (fcc) FeMn thin films are successfully obtained with use of a Cu seed layer covering with the Al2O3 surface, while nonmagnetic α-phase (bcc) FeMn thin films are formed without a Cu seed layer. When the sputtering temperature is set at 500 °C, γ-FeMn films grown on Cu/Al2O3 are highly oriented along the (111) plane, but minor α-Fe phases are included owing to alloying with the Cu layer. Ferromagnetic transports of α-Fe phases are observed in Hall and Nernst effects at low magnetic fields. By contrast, the slope of Hall conductivity at high magnetic fields is found to be several times larger for the γ-FeMn phase than for the α-FeMn phase, which suggests that the antiferromagnetic spin structure of γ-FeMn contributes to the Hall effect.