The anomalous Hall effect (AHE) has been understood as a transport phenomenon usually observed in ferromagnetic and non-collinear antiferromagnetic materials where broken time-reversal symmetry combined with spin-orbit coupling produces a net Berry curvature. Combined spatial inversion (P) and time-reversal (T) symmetries forbid an AHE in collinear antiferromagnets. In this study, we demonstrate a pronounced AHE in (110)-oriented FeRh thin films epitaxially grown on Al2O3 substrates, even though the films remain collinear antiferromagnetic at low temperatures. Unlike the bulk B2 phase, where PT symmetry enforces the cancellation of Berry curvature, the epitaxial (110) orientation and substrate-induced strain explicitly break the spatial inversion symmetry (P). This symmetry-lowering mechanism, which lifts the PT constraint, enables a finite Berry curvature distribution in momentum space. Consequently, this allows for robust anomalous transverse transport even in the collinear antiferromagnetic regime, providing a new degree of freedom to engineer topological properties in antiferromagnets. First-principles density-functional calculations reproduce the strain-induced Berry curvature and quantitatively account for the measured AHE in the 5-100 K range. Our results show that intrinsic strain can be harnessed to tailor Berry curvature in collinear antiferromagnets, opening a pathway toward antiferromagnetic spintronic applications.
Kim et al. (Wed,) studied this question.