Influence of magnetic anisotropy on the Kondo effect and spin-polarized transport through magnetic molecules, adatoms, and quantum dots

Transport properties in the Kondo regime of a nanosystem displaying uniaxial magnetic anisotropy (such as a magnetic molecule, magnetic adatom, or quantum dot coupled to a localized magnetic moment) are analyzed theoretically. In particular, the influence of spin-polarized transport through a local orbital of the system and exchange coupling of conduction electrons to the system's magnetic core on the Kondo effect is discussed. The numerical renormalization-group method is applied to calculate the spectral functions and linear conductance in the case of the parallel and antiparallel configurations of the electrodes' magnetic moments. It is shown that both the magnetic anisotropy as well as the exchange coupling between electrons tunneling through the conducting orbital and magnetic core play an important role in the formation of the Kondo resonance, leading generally to its suppression. Specific transport properties of such a system appear also as a nontrivial behavior of tunnel magnetoresistance. It is also shown that the Kondo effect can be restored by an external magnetic field in both the parallel and antiparallel magnetic configurations.