Observation of a Positive Hyperfine Field for Dilute Fe Impurities in Ca

Abstract

The magnetic hyperfine field for isolated Fe impurities in Ca metal has been measured as a function of temperature ($86 \mathrm{K}<~T<~300 \mathrm{K}$) by use of the technique of perturbed angular distributions. The data indicate the presence of an unquenched orbital local moment. This is the first such observation for Fe impurities in any metal host. The results could not be explained by the assumption of a purely ionic configuration for the impurity and are interpreted in terms of the Friedel-Anderson model.