Magnetic Imaging and Domain Nucleation in CrSBr Down to the 2D Limit.

Recent advancements in two-dimensional (2D) materials have revealed the potential of van der Waals magnets, and specifically of their magnetic anisotropy that allows applications down to the two-dimensional limit. Among these materials, CrSBr has emerged as a promising candidate, because its intriguing magnetic and electronic properties have appeal for both fundamental and applied research in spintronics or magnonics. Here, we use nano SQUID-on-tip (SOT) microscopy to obtain direct magnetic imaging of CrSBr flakes with thicknesses ranging from monolayer (N = 1) to few-layer (N = 5). The ferromagnetic order is preserved down to the monolayer, while the antiferromagnetic coupling of the layers starts from the bilayer case. For odd layers, at zero applied magnetic field, we directly image the stray field resulting from the uncompensated layer. We also measure the progressive spin reorientation along the out-of-plane direction (hard axis) with a finite applied magnetic field, allowing us to evaluate the anisotropy constant, which remains stable down to the monolayer and is close to the bulk value. Finally, by controlling the size of the applied magnetic field, we can observe the formation of Néel magnetic domain walls down to the single layer limit. This article is protected by copyright. All rights reserved.