Properties of anisotropic magnetic impurities on surfaces

Rok Zitko; Robert Peters; Thomas Pruschke

doi:10.1103/PhysRevB.78.224404

paper

Properties of anisotropic magnetic impurities on surfaces

arXiv:0809.0759 · doi:10.1103/PhysRevB.78.224404

Abstract

Using numerical renormalization group techniques, we study static and dynamic properties of a family of single-channel Kondo impurity models with axial magnetic anisotropy $D S_{z}^{2}$ terms; such models are appropriate to describe magnetic impurity atoms adsorbed on non-magnetic surfaces, which may exhibit surface Kondo effect. We show that for positive anisotropy $D$ and for any spin $S$ , the systems behave at low temperatures as regular Fermi liquids with fully compensated impurity spin. The approach to the stable fixed point depends on the value of the spin $S$ and on the ratio $D / T_{K}^{(0)}$ , where $T_{K}^{(0)}$ is the Kondo temperature in the absence of the anisotropy. For S=1, the screening occurs in two stages if $D < T_{K}^{(0)}$ ; the second Kondo temperature is exponentially reduced in this case. More generally, there is an effective spin-1/2 Kondo effect for any integer $S$ if $D < T_{K}^{(0)}$ and for any half-integer $S$ if $D > T_{K}^{(0)}$ . For negative anisotropy $D$ , the system is a non-Fermi liquid with residual anisotropic exchange interaction. However, the presence of transverse magnetic anisotropy $E (S_{x}^{2} - S_{y}^{2})$ restores Fermi-liquid behavior in real systems.

14 pages, 12 figures

Properties of anisotropic magnetic impurities on surfaces

Abstract

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