Carrier-induced phase transition in metal dichlorides XCl2 (X: Fe, Co, and Ni)

We investigated the ground state of monolayer 1T-XCl$_{2}$ (X: Fe, Co, and Ni) using generalized Bloch theorem, which can generate ferromagnetic, spiral, antiferromagnetic states. Each was represented by a unique spiral vector that arranges magnetic moment atom in primitive unit cell. found ferromagnetic for FeCl$_{2}$ NiCl$_{2}$ while appears CoCl$_{2}$. also showed depends sensitively on lattice constant. When hole-electron doping taken into account, we phase transition, involves states, all systems. Since spin-spin interaction metal dichlorides is influenced competition between direct exchange superexchange, justify carrier concentration determines should dominate.