Surface Magnetic Anisotropy of Kondo Impurities Induced by Spin-Orbit Scattering

Abstract

In the last decade, many experiments [1, 2, 3, 4] were performed on thin films and narrow wires of dilute magnetic alloys (e.g. Au(Fe), Cu(Fe), Cu(Cr)). The motivation of these experiments was the searching for the Kondo compensation cloud [5] as it became easy to prepare mesoscopic samples with size comparable or even smaller than the estimated size of the Kondo coherence length [5]. They found no essential change in the Kondo temperature, however, in most of the experiments [1, 2] a suppression of the Kondo resistivity amplitude was observed for small sample sizes (see Fig. 1). Covering the thin films of magnetic alloys by another pure metal layer, a partial recovery of the Kondo signal was found (proximity effect; see Fig. 2(a)) [6, 7] which was smaller for more disordered overlayers [8]. The first natural explanation [9] that the compensation cloud cannot be fully developed if the sample size at least in one dimension is smaller than the size of the cloud, was ruled out both theoretically [10, 11] and experimentally [7]. The possibility of changes in the local density of states by Friedel oscillations due to the surface was also ruled out [11] as they are localized in a few atomic distances from the surface.