Atomistic Engineering of Anisotropic 2D vdW Magnets

The exploration of 1D magnetism, frequently portrayed as spin chains, constitutes an actively pursued research field that illuminates fundamental principles in many-body problems and applications in magnonics and spintronics. The inherent reduction in dimensionality often leads to robust spin fluctuations, impacting magnetic ordering and resulting in novel magnetic phenomena. Here, structural, magnetic, and optical properties of highly anisotropic 2D van der Waals antiferromagnets that uniquely host spin chains are explored. First-principle calculations reveal that the weakest interaction is interchain, leading to essentially 1D magnetic behavior in each layer. With the additional degree of freedom arising from its anisotropic structure, the structure is engineered by alloying, varying the 1D spin chain lengths using electron beam irradiation, or twisting for localized patterning, and spin textures are calculated, predicting robust stability of the antiferromagnetic ordering. Comparing with other spin chain magnets, these materials are anticipated to bring fresh perspectives on harvesting low-dimensional magnetism.¹<br/> <br/>Here, we examine the structural properties of two kinds of 2D magnets hosting 1D chains of magnetic atoms. Using scanning transmission electron microscopy (STEM), we characterize structural properties such as the alignment of magnetic chains between layers with atomic resolution. We also explore the nature of defects and the possibility of controlling defect location using the STEM electron beam.^2,3 By parametrizing a model spin-Hamiltonian based on density functional theory calculations, we predict the spin structure that develops from the chain arrangement of the magnetic atoms in this material. We discuss measurements to verify theoretical calculations using instruments such as vibrating sample magnetometry. Lastly, we engineer the 2D magnet via electron beam irradiation to modify the structure of 1D spin chains and predict magnetic properties and spin structure using atomistic magnetic simulation.<br/> <br/>References<br/>1. Park, E., Philbin, J. P., Chi, H. <i>et al</i>. Anisotropic 2D van der Waals Magnets Hosting 1D Spin Chains, <i>Advanced Materials</i> 202401534 (2024)<br/>2. Klein, J., Pingault, B., Florian, M. <i>et al</i>. The bulk van der Waals layered magnet CrSBr is a quasi-1D quantum material. <i>ACS nano</i> <b>17</b>, 5316-5328 (2023).<br/>3. Klein, J., Pham, T., Thomsen, J. D. <i>et al.</i> Control of structure and spin texture in the van der Waals layered magnet CrSBr, <i>Nature Communications</i> <b>13</b>, 5420 (2022).