Instability of the magnetic state of MPX3(M=Mn,Ni;X=S,Se) monolayers induced by strain and doping

The instability of magnetic states in two-dimensional magnetic materials plays a crucial role in the application of spintronics. However, the instability mechanism and magnetic state diagram of $M\text{P}{X}₃$ ($M=\mathrm{Mn}$ and Ni and $X=\mathrm{S}$ and Se) monolayer with multiple magnetic states remains elusive. In our paper, we investigate the instability of magnetic states using ab initio calculation combined with an effective Heisenberg model. We obtain a series of magnetic state diagrams of $M\text{P}{X}₃$ ($M=\mathrm{Mn}$ and Ni and $X=\mathrm{S}$ and Se) monolayer under the approaches of strain and carrier doping. We clarify the instability mechanism that is mainly determined by the nearest-neighbor exchange interaction between magnetic ions, find a higher N\'eel temperature in ${\mathrm{NiPSe}}₃$ monolayer, and unveil a considerable increase in hole effective mass along the armchair direction in the ${\mathrm{NiPSe}}₃$ monolayer, which leads to giant anisotropy of carrier mobility. Our results provide a useful guidance to design high-performance spintronics devices based on the $M\text{P}{X}₃$ monolayer.