The monolayer halides CrX3 (X=Cl, Br, I) attract significant attention for realizing 2D magnets with genuine long-range order (LRO), challenging the Mermin-Wagner theorem. Here, we show that monolayer CrCl3 has the unique benefit of exhibiting tunable magnetic anisotropy upon applying a compressive strain. This opens the possibility to use CrCl3 for producing and studying both ferromagnetic and antiferromagnetic 2D Ising-type LRO as well as the Berezinskii-Kosterlitz-Thouless (BKT) regime of 2D magnetism with quasi-LRO. Using state-of-the-art density functional theory, we explain how realistic compressive strain could be used to tune the monolayer's magnetic properties so that it could exhibit any of these phases. Building on large-scale quantum Monte Carlo simulations, we compute the phase diagram of strained CrCl3, as well as the magnon spectrum with spin-wave theory. Our results highlight the eminent suitability of monolayer CrCl3 to achieve very high BKT transition temperatures, around 50 K, due to their singular dependence on the weak easy-plane anisotropy of the material.
@article{arxiv.2012.12801,
title = {Monolayer CrCl$_3$ as an ideal Test Bed for the Universality Classes of 2D Magnetism},
author = {Maxime Dupont and Yaroslav O. Kvashnin and Mahroo Shiranzaei and Jonas Fransson and Nicolas Laflorencie and Adrian Kantian},
journal= {arXiv preprint arXiv:2012.12801},
year = {2021}
}