Longitudinal and transverse spin relaxation times of magnetic single adatoms: An ab initio analysis

摘要

We present a systematic ab initio investigation of the longitudinal and transverse spin relaxation times of magnetic single adatoms deposited on metallic substrates. Our analysis based on time-dependent density functional theory shows that the longitudinal time 7j| is of order femtosecond while the transverse time T_⊥ is of order picosecond, i.e. T_⊥ » T_‖. This comes as a consequence of the different energy scales of the corresponding processes: T_‖ involves spin-density excitations of order eV, while T± is governed by atomic spin excitations of order meV. Comparison to available inelastic scanning tunneling spectroscopy dI/dV experimental curves shows that the order of magnitude of T_⊥agrees well with our results. Regarding T_‖, the time scale calculated here is several orders of magnitude faster than what has been measured up to now; we therefore propose that an ultrafast laser pulse measuring technique is required in order to access the ultrafast spin dynamics described in this paper.