Magneto-optical Kerr effect in an A-type antiferromagnet Sunko, Veronika ; https://orcid.org/0000-0003-2724-3523 Ahsanullah, Salman Jain, Vivek Weber, Sophie Kumaran, Sivaloganathan Yan, Jiaqiang Orenstein, Joseph Ovchinnikov, Dmitry ddc:530 Magneto-optic Kerr effect (MOKE) is a powerful probe of broken time-reversal symmetry (T), typically used to study ferromagnets. While MOKE has been observed in some antiferromagnets (AFMs) with vanishing magnetization, it is often associated with structures whose symmetry is lower than basic collinear, bipartite order. In contrast, theory predicts a mechanism for MOKE intrinsic to all AFMs of A-type, i.e. layered AFMs in which ferromagnetic layers are antiferromagnetically aligned. Here we report the experimental confirmation of this mechanism in a bulk AFM. We achieve this by measuring the imaginary component of MOKE as a function of photon energy in MnBi2Te4, an A-type AFM where T is preserved in combination with a translation, and comparing the experimental results with model calculations. Our model suggests that observable MOKE should be expected in all collinear A-type AFMs with out-of-plane spin order, thus enabling optical detection of AFM domains and expanding the scope of MOKE to few-layer AFMs. Springer Nature 2026 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/21872 Sunko V, Ahsanullah S, Jain V, et al. Magneto-optical Kerr effect in an A-type antiferromagnet. <i>Nature Communications</i>. 2026. doi:<a href="https://doi.org/10.1038/s41467-026-72577-4">10.1038/s41467-026-72577-4</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1038/s41467-026-72577-4 info:eu-repo/semantics/altIdentifier/e-issn/2041-1723 info:eu-repo/semantics/openAccess