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E. Kirstein1, H. Park2,3, I. Martin2, J. F. Mitchell2, N. J. Ghimire4,5, and S. A. Crooker1

• 1National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
• 2Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
• 3Department of Physics, University of Illinois Chicago, Chicago, Illinois 60607, USA
• 4Department of Physics and Astronomy, Notre Dame University, Notre Dame, Indiana 46556, USA
• 5Stavropoulos Center for Complex Quantum Matter, Notre Dame University, Notre Dame, IN, 46556, USA

Abstract

Despite its tiny net magnetization, the antiferromagnetic (AFM) van der Waals material Co1/3NbS2 exhibits a large transverse Hall conductivity σxy even at zero applied magnetic field, which arises, as recently shown, from the topological nature of its noncoplanar “tetrahedral” AFM order. This triple-q magnetic order can be regarded as the short-length-scale limit of a magnetic skyrmion lattice and has an intrinsic spin chirality. Here, we show, using optical wavelengths spanning the ultraviolet to infrared (400–1000 nm), that magnetic circular dichroism provides an incisive optical probe of the topological AFM order in Co1/3NbS2. Measurements as a continuous function of photon energy are directly compared with first-principles calculations, revealing the influence of the underlying quantum geometry on optical conductivity. Leveraging the power and flexibility of optical methods, we use scanning magnetic circular dichroism microscopy to directly image chiral AFM domains and demonstrate writing of chiral AFM domains.

• Magnetic domains
• Topological Hall effect
• Antiferromagnets
• Noncollinear magnets
• Triangular lattice
• Magneto-optical Kerr effect

synopsis

Shining Light on Antiferromagnets

Published 4 November, 2025

Researchers use a magneto-optical technique to image and manipulate magnetic domains in a chiral antiferromagnet, opening new routes for spin-based electronics.

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