The magneto-optical Kerr effect (MOKE) is investigated in hematite, a collinear antiferromagnetic insulator, across a broad wavelength spectrum. By combining the optical measurements with magnetometry results, we unambiguously demonstrate that the N\'eel-order contribution dominates the MOKE signal, while contributions from net magnetization and external magnetic fields are negligible. This conclusion is quantitatively supported by first-principles calculations, and qualitatively by a symmetry analysis that the N\'eel contribution appears at the first order in spin-orbit coupling while the magnetization contribution starts only at the third order. This study clarifies the altermagnetic origin of the pronounced MOKE in hematite, underscoring the potential of altermagnets as a promising new class of magneto-optical materials.
@article{arxiv.2512.07149,
title = {Experimental Evidence of N\'eel-order-driven Magneto-optical Kerr Effect in an Altermagnetic Insulator},
author = {Haolin Pan and Rui-Chun Xiao and Jiahao Han and Hongxing Zhu and Junxue Li and Qian Niu and Yang Gao and Dazhi Hou},
journal= {arXiv preprint arXiv:2512.07149},
year = {2025}
}