Dynamic magnetic excitations in 3d and 4f atoms and clusters

Spins in magnetic nanostructures can be excited by an electric current. In the inelastic scattering events, the spin of a tunneling electron provided by a scanning tunneling microscope may be flipped and angular momentum is transferred to the magnetic system. We used this technique to determine magnetic anisotropies and exchange couplings in 3d transition and 4f rare earth metal atoms and clusters on surfaces. Further, we discuss that the magnetic anisotropy, i.e. the zero field splitting, in rare earth atoms requires a fully relativistic description, in which not only the spin of the atoms but also their orbital angular momentum is taken into account. When describing the magnetic anisotropy with the Hamiltonian including all Stevens operators and combining it with spin flip scattering by conduction and tunneling electrons, we find that long spin lifetimes are theoretically expected for specific total angular momenta and crystal field symmetries and show experimental evidence that such a situation is realized in Ho on Pt(111).