Strain-Tunable Anomalous Hall Plateau in Antiferromagnet CoNb₃S₆

Antiferromagnets with anomalous Hall effects offer a compelling link among magnetism, topology, and electronic structure. Identifying antiferromagnets with large and tunable anomalous Hall effects is crucial for the development of spintronic applications. We report a strain-tunable anomalous Hall plateau in CoNb₃S₆, a layered antiferromagnet known for its unexpectedly large anomalous Hall conductivity. The plateau emerges as a flat, extended intermediate step in the Hall hysteresis loop with the step height tunable by temperature and strain. Unlike typical magnetic plateaus tied to metastable states, this behavior suggests a hidden phase transition that alters magnetic anisotropy without changing the magnetic order. Symmetry analysis suggests that the hidden phase preserves the rotational symmetry of the ab plane. The plateau reflects phase coexistence during the hidden transition and exhibits non-volatile anomalous Hall resistivity, enabling a novel four-state Hall switching.