Beyond the upper limit of magnetic anisotropy in two-dimensional transition metal dichalcogenides

Exploring an upper limit of magnetic anisotropy in two-dimensional materials, such as graphene and transition metal dichalcogenides, is at the heart of spintronics research. Herein, an atomic-scale perpendicular magnetic anisotropy up to an order of 100 meV per atom, which is far beyond the ordinarily obtained value in graphene and pristine transition metal dichalcogenides, is demonstrated in individual ruthenium and osmium adatoms at a monosulfur vacancy in molybdenum disulfide. We further propose a phenomenological model where a spin state transition that involves hybridization between molybdenum a1 and adatomic e' orbitals is a possible mechanism for magnetization reorientation.