We analyze magnetic phases of monolayers of transition metal dichalcogenides that are two-valley materials with electron-electron interactions. The exchange inter-valley scattering makes two-valley systems less stable to the spin fluctuations but more stable to the valley fluctuations. We predict a first order ferromagnetic phase transition governed by the non-analytic and negative cubic term in the free energy that results in a large spontaneous spin magnetization. Finite spin-orbit interaction leads to the out-of-plane Ising order of the ferromagnetic phase. Our theoretical prediction is consistent with the recent experiment on electron-doped monolayers of MoS2 reported by Roch et al. [1]. The proposed first order phase transition can also be tested by measuring the linear magnetic field dependence of the spin susceptibility in the paramagnetic phase which is a direct consequence of the non-analyticity of the free energy.
@article{arxiv.1902.07961,
title = {Exchange Intervalley Scattering And Magnetic Phase Diagram Of Transition Metal Dichalcogenide Monolayers},
author = {Dmitry Miserev and Jelena Klinovaja and Daniel Loss},
journal= {arXiv preprint arXiv:1902.07961},
year = {2019}
}