Spin-crossover and massive anisotropy switching of 5d transition metal atoms on graphene nanoflakes.

In spin crossover phenomena, the magnetic moment of a molecule is switched by external means. Here we theoretically predict that several 5d-transition metals (TMs) adsorbed on finite graphene flakes undergo a spin crossover, resulting from multiple adsorption minima, that are absent in the zero-dimensional limit of benzene and the two-dimensional limit of graphene. The different spin states are stable at finite temperature and can be reversibly switched with an electric field. The system undergoes a change in magnetic anisotropy upon spin crossover, which facilitates read-out of the spin state. The TM-decorated nanoflakes thus act as fully controlled single-ion magnetic switches.