Supporting Information

Exfoliation energy of monolayer MnTiF2. Inset is side view of bulk MnTiF2 and interlayer distance; Phonon spectra of monolayers MnTiCl2 and MnTiBr2; Magnetic configurations FM, AFM1, AFM2 and AFM3 of monolayers MnTiX2; The PDOS of monolayers MnTiCl2 and MnTiBr2. Angular dependence of MAEs of the MnTiCl2 and MnTiBr2 monolayers with the directions of magnetization lying on the whole space. The band structures of MnTiCl2 and MnTiBr2 monolayers without SOC. The band structures of MnTiCl2 and MnTiBr2 monolayers considering SOC, the edge states of MnTiCl2 and MnTiBr2 monolayers, the AHCs of MnTiCl2 and MnTiBr2 monolayers with the magnetic direction along the z axis. The band structures with SOC with the magnetic direction along the z axis of MnTiCl2 and MnTiBr2 monolayers, the valley polarizations of valance bands of them. The band structures the valley polarizations at the VBM of MnTiF2 monolayer considering SOC with the magnetic direction along the z axis within 6% strain. The exchange parameter and the magnetic anisotropic energies MAEs.