Toward intrinsic ultra-high-temperature ferromagnetism in a CrAuTe2/graphene heterosystem.

Exploring intrinsic two-dimensional (2D) ferromagnetic (FM) materials with high Curie temperatures (TC) and large magnetic anisotropy energies (MAE) is one of the effective solutions to develop materials for high-performance spintronic applications. Using density functional theory calculations and high-throughput computations, we predict an intrinsic bimetallic FM monolayer, CrAuTe2, which has a large MAE and high TC. The results show that the value of the MAE can reach about 1.5 meV per Cr, and Monte Carlo simulations show that the TC of monolayer CrAuTe2 is about 840 K. Further analysis indicates that the joint effects of spin-orbit coupling (SOC) interaction and magnetic dipole-dipole interaction result in high in-plane magnetic anisotropy. In addition, this monolayer has good dynamic, thermal, and mechanical stabilities, which were confirmed by ab initio molecular dynamics simulations, phonon spectra, and elastic constants, respectively. In order to propose a practical synthesis approach, we built a CrAuTe2/graphene van der Waals heterostructure, and found that the heterostructure does not affect the magnetic properties of monolayer CrAuTe2. These findings appear promising for the future applications in nano-spintronics.

High temperature ferromagnetic metal: a Janus CrSSe monolayer.

Two-dimensional (2D) ferromagnets are popular in fields such as spintronic devices, but their low Curie temperature (TC) limits their practical application. In this work, by using a global optimization evolutionary algorithm and density functional theory method, a Janus CrSSe ferromagnetic monolayer was predicted systematically. Monte Carlo simulations show that the Curie temperature of the Janus CrSSe monolayer is about 272 K and can be adjusted to 496 K under a small tensile biaxial strain. Besides, this monolayer possesses large magnetic anisotropy energy (1.4 meV Cr-1). The magnetic order can be changed from ferromagnetic to antiferromagnetic order under compressive strain. What's more, this monolayer possesses the lowest energy in the 2D search space and excellent thermal, dynamic, and mechanical stabilities. Considering its excellent properties and current experimental techniques, it is possible to synthesize CrSSe monolayer experimentally.

Origin and regulation of triaxial magnetic anisotropy in the ferromagnetic semiconductor CrSBr monolayer.

Magnetic anisotropy plays a vital role in stabilizing the long-range magnetic order of two-dimensional ferromagnetic systems. In this work, using the first-principles method, we systematically explored the triaxial magnetic anisotropic properties of a ferromagnetic semiconductor CrSBr monolayer, which is recently exfoliated from its bulk. Further analysis shows that the triaxial magnetic anisotropic properties originate from the coexistence of the magnetic dipole-dipole interaction (shape anisotropy) and the spin-orbit coupling interaction (magnetocrystalline anisotropy). Interestingly, the shape anisotropy, which has been neglected in most previous works, dominates over the magnetocrystalline anisotropy. Besides, the experimental Curie temperature of the CrSBr monolayer is well reproduced using Monte Carlo simulations. What is more, the easy magnetic axes and ferromagnetism in the CrSBr monolayer can be manipulated by strains and are relatively more susceptible to the uniaxial strain in the x direction. Our study not only explains the mechanism of triaxial magnetic anisotropy of the CrSBr monolayer, but also sheds light on how to tune the magnetic anisotropy and Curie temperature in ferromagnetic monolayers.