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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>T</mml:mi></mml:math>. 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 L1₀-IrMn (001) film. Scanning transmission electron microscopy investigation shows the presence of (200)-oriented grains in the L1₀-IrMn (001)-oriented film due to the large lattice mismatch between the films and substrate. Consequently, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>t</mml:mi></mml:mrow><mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mrow></mml:msub><mml:mi>T</mml:mi></mml:math> joint symmetry, with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>t</mml:mi></mml:mrow><mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mrow></mml:msub></mml:math> 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.