Observation of Anomalous Hall Effect in Collinear Antiferromagnet IrMn.

The anomalous Hall effect (AHE) is a transport phenomenon typically observed in ferromagnetic materials with broken time-reversal symmetry . Recently, the AHE has been observed in several archetype antiferromagnets (AFMs), including altermagnets, and AFMs with noncollinear, noncoplanar or canted Néel order, due to the breaking of joint symmetry of sublattice-transposing and time-reversal operation. However, the AHE is generally not allowed in collinear AFMs due to symmetry constraints. Here, we report the observation of the AHE in a collinear AFM L1-IrMn (001) film. Scanning transmission electron microscopy investigation shows the presence of (200)-oriented grains in the L1-IrMn (001)-oriented film due to the large lattice mismatch between the films and substrate. Consequently, the joint symmetry, with being the translation operation, may be locally broken in our samples, thus enabling the AHE, which is further supported by ab initio calculations. Our work provides a novel way to generate the AHE in AFMs by engineering the local symmetry.