Revealing the Altermagnetism in Hematite via XMCD Imaging and Anomalous Hall Electrical Transport

Altermagnets are a class of magnetic materials that exhibit unconventional transport properties, such as an anomalous Hall effect (AHE), despite having compensated sublattice magnetic moments. In this study, fundamental experimental evidence of the altermagnetic nature of hematite (α-Fe₂O₃), is reported combining electrical transport with advanced X-ray photoemission electron microscopy (XPEEM) imaging with linear and circular dichroism contrast. These measurements directly visualize the Néel vector's coupling to the crystal orientation, confirming hematite's altermagnetic order and its symmetry-driven transport behavior. The transport measurements reveal an anisotropic AHE with a pronounced crystal orientation dependence, including a sign inversion for specific Néel vector alignments. Supported by first-principles theoretical calculations, how the interplay between collinear spin and crystal symmetry breaking drives the observed AHE is explained. These findings establish hematite as an altermagnet, paving the way for experimental identification of altermagnetic materials and their integration into spintronic technologies.