Role of charge doping and strain in the stabilization of in-plane ferromagnetism in monolayer V S e 2 at room temperature

We study the origin of in-plane ferromagnetism in monolayer VSe 2 focusing on the effect of charge doping and mechanical strain. We start from an anisotropic spin Hamiltonian, estimate its parameters from density functional calculations, and determine the spectrum of spin-wave excitations. We show that 1T-VSe 2 is characterized by relatively strong on-site Coulomb repulsion ( U ≃ 5 eV), favoring an antiferromagnetic ground state, which contradicts experimental observations. We calculate the magnetic phase diagram as a function of charge doping and strain, and find a transition to the ferromagnetic state with in-plane easy axis under moderate hole doping (∼10 14 cm −2 ). Analysis of spin-wave excitations in doped monolayer VSe 2 reveals a gap due to the in-plane anisotropy, giving rise to long-range magnetic order well above 300 K, in agreement with recent experiments. Our findings suggest that experimentally available 1T-VSe 2 monolayer samples might be intrinsically or extrinsically doped, which opens up the possibility for a controllable manipulation of their magnetic properties.