Van der Waals (vdW) magnetic materials are comprised of layers of atomically thin sheets, making them ideal platforms for studying magnetism at the two-dimensional (2D) limit. These materials are at the center of a host of novel types of experiments, however, there are notably few pathways to directly probe their magnetic structure. We report the magnetic order within a single crystal of NiPS3 and show it can be accessed with resonant elastic X-ray diffraction along the edge of the vdW planes in a carefully grown crystal by detecting structurally forbidden resonant magnetic X-ray scattering. We find the magnetic order parameter has a critical exponent of β∼0.36, indicating that the magnetism of these vdW crystals is more adequately characterized by the three-dimensional (3D) Heisenberg universality class. We verify these findings with first-principle density functional theory, Monte-Carlo simulations, and density matrix renormalization group calculations.
@article{arxiv.2310.07948,
title = {3D Heisenberg universality in the Van der Waals antiferromagnet NiPS$_3$},
author = {Rajan Plumley and Sougata Mardanya and Cheng Peng and Johannes Nokelainen and Tadesse Assefa and Lingjia Shen and Nicholas Burdet and Zach Porter and Alexander Petsch and Aidan Israelski and Hongwei Chen and Jun Sik Lee and Sophie Morley and Sujoy Roy and Gilberto Fabbris and Elizabeth Blackburn and Adrian Feiguin and Arun Bansil and Wei-Sheng Lee and Aaron Lindenberg and Sugata Chowdhury and Mike Dunne and Joshua J. Turner},
journal= {arXiv preprint arXiv:2310.07948},
year = {2024}
}