Kondo effect on the resistivity of Au:Gd and on the ESR of Au:Yb

Abstract
The resistivity of 5000 ppm atomic Gd in Au is observed to decrease with decreasing temperature from 4.2 to 1K, a behavior typical of ferromagnetic (Jeff≳0) Kondo effect. The scaling parameter TK is found to be ∼108K and N(EF)Jo is compared to ESR result. Spin‐spin interaction is also evident in the resistivity below 2K. ESR measurements on dilute Au:Yb alloys from 100 mK to 4K and at microwave frequencies of 3 and 9 GHz show for the first time a logarithmic temperature dependence for both the g‐shift and the relaxation rate. The results yield a Kondo temperature TK∼10μK and a degeneracy of d∼3 for the local moment‐conduction electron interaction channels.