Superexchange Interactions and Magnetic Anisotropy in MnPSe$_3$ Monolayer
Guangyu Wang1,2†, Ke Yang3,1†, Yaozhenghang Ma1,2, Lu Liu1,2, Di Lu1,2, Yuxuan Zhou1,2, and Hua Wu1,2,4*
1Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, China 2Shanghai Qi Zhi Institute, Shanghai 200232, China 3College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China 4Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
Abstract：Two-dimensional van der Waals magnetic materials are of great current interest for their promising applications in spintronics. Using density functional theory calculations in combination with the maximally localized Wannier functions method and the magnetic anisotropy analyses, we study the electronic and magnetic properties of MnPSe$_3$ monolayer. Our results show that it is a charge transfer antiferromagnetic (AF) insulator. For this Mn$^{2+}$ $3d^5$ system, although it seems straightforward to explain the AF ground state using the direct exchange, we find that the nearly 90$^\circ$ Mn–Se–Mn charge transfer type superexchange plays a dominant role in stabilizing the AF ground state. Moreover, our results indicate that, although the shape anisotropy favors an out-of-plane spin orientation, the spin-orbit coupling (SOC) leads to the experimentally observed in-plane spin orientation. We prove that the actual dominant contribution to the magnetic anisotropy comes from the second-order perturbation of the SOC, by analyzing its distribution over the reciprocal space. Using the AF exchange and anisotropy parameters obtained from our calculations, our Monte Carlo simulations give the Néel temperature $T_{\rm N}=47$ K for MnPSe$_3$ monolayer, which agrees with the experimental 40 K. Furthermore, our calculations show that under a uniaxial tensile (compressive) strain, Néel vector would be parallel (perpendicular) to the strain direction, which well reproduces the recent experiments. We also predict that $T_{\rm N}$ would be increased by a compressive strain.
. [J]. 中国物理快报, 2023, 40(7): 77301-.
Guangyu Wang, Ke Yang, Yaozhenghang Ma, Lu Liu, Di Lu, Yuxuan Zhou, and Hua Wu. Superexchange Interactions and Magnetic Anisotropy in MnPSe$_3$ Monolayer. Chin. Phys. Lett., 2023, 40(7): 77301-.
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See the Supplemental Materials for the calculation of the magnetic exchange parameters, the hopping integrals of spin-up channels, the distributions of the MAE in the FM state over the reciprocal space, and the polar diagrams of the MAE under strains.
2023, Vol. 40 
