Stable antiferromagnetic property and tunable electronic structure of two-dimensional MnPX3(X = S and Se) from pristine structure to Janus phase

Abstract

Transition-metal phosphorus trichalcogenides have been considered as very promising two-dimensional (2D) magnetic candidates up-to-date. We performed a systematical first-principles study on the electronic structures and magnetic properties of pristine MnPX₃(X = S and Se) and Janus Mn₂P₂S₃Se₃monolayers. All monolayers behave as a direct-band-gap semiconductor in antiferromagnetic ground state which is caused by strong direct and indirect exchange interactions. It is found that the electronic structures and magnetic properties can be manipulated by Janus phase. The calculated band gap is 2.44 eV, 1.80 eV and 1.86 eV for MnPS₃, MnPSe₃and Mn₂P₂S₃Se₃with a valley polarization with consideration of spin-orbital coupling (SOC), respectively. In particular, significant energy-splittings emerge in the SOC-band structures of Janus Mn₂P₂S₃Se₃due to its broken-inversion-symmetry. Estimated by Monte Carlo simulations, the Néel temperature is 96 K, 71 K and 79 K based on Ising model while halved down to 41 K, 33 K and 36 K on the basis ofXYmodel for MnPS₃, MnPSe₃and Mn₂P₂S₃Se₃, respectively, indicating theXYmodel should be more reliable to describe the spin dynamics. Our research offers an insight into the magnetic mechanism and paves a feasible path to modulate the magnetism for 2D magnets in realistic applications on spintronics.

Keywords: 2D magnetic materials; Monte Carlo simulations; first-principles calculations; transition-metal phosphorus trichalcogenides.