Nanoscale antiferromagnetic domain imaging using full‐field resonant x‐ray magnetic diffraction microscopy

The physical properties of magnetic materials frequently depend not only on the microscopic spin and electronic structures, but also on the structures of mesoscopic length scales that emerge, for instance, from domain formations, chemical and/or electronic phase separations. However, experimental access to such mesoscopic structures is currently limited, especially for antiferromagnets (AF) with net zero magnetizations. Here, we combine full-field microscopy and resonant magnetic x-ray diffraction to visualize AF domains of the spin-orbit Mott insulator Sr2 IrO4 over ∼0.1 mm2 area with the spatial resolution as high as ∼150 nm. With the unprecedented wide field of views and high spatial resolutions, we reveal an intertwining of two AF domains on a length comparable to the measured average AF domain wall width of 545 nm. This mesoscopic structure comprises a substantial portion of the sample surface, and thus can result in a macroscopic response that is unexpected from its microscopic magnetic structure. In particular, our symmetry analysis shows that the inversion symmetry, which is preserved by the microscopic AF order, becomes ill defined in the mesoscopic length scale. This result underscores the importance of our novel technique for a thorough understanding of the physical properties of antiferromagnets. This article is protected by copyright. All rights reserved.