Anomalous Hall magnetoresistance in metastable antiferromagnetic FeMn

Anomalous Hall magnetoresistance (AHMR) in single ferromagnetic layers arises from anomalous Hall effect induced spin current and its backflow. Here, we have studied the correlation between AHMR and weak ferromagnetism as well as the antiferromagnetic property in metastable FeMn layers. The ferromagnetic and the antiferromagnetic properties are tuned by the FeMn microstructure through varying the Cu buffer layer thickness. With increasing Cu thickness, both the anomalous Hall angle and the AHMR are suppressed as the content of the parasitic ferromagnet becomes low and the antiferromagnetic order strengthens in FeMn. The exchange bias in Co/FeMn further evidences the evolution of FeMn properties with Cu buffer layer thickness. Our results are in agreement with the theoretical prediction of the AHMR and help the understanding of spin current related phenomena in metastable antiferromagnetic materials.