Size effects on the magnetic hyperfine fields at non-magnetic impurities in iron

Abstract

An important contribution to the magnetic hyperfine fields at non-magnetic impurities in magnetic metals arises from the conduction-electron polarization (CEP). In the model of Stearns the CEP at the impurity site,Pce, arises from the exchange interaction of the conduction electrons at that site with the localized 3d host electrons. In this modelPce is a negative constant, independent of the impurity, so that an emperical volume-misfit correction has to be introduced to explain the observed positive hyperfine fields. The purpose of this paper is to show thatPce is not constant, but is strongly affected by the distortion of the lattice around the impurity. The correct form ofPce includes a volume term equivalent to that postulated by Stearns. The hyperfine fields for Cu, Zn, Sn, Sb and Au are calculated, taking the distortion effects into account. A fair agreement with the observed hyperfine fields is obtained. Furthermore, the effects of pressure on the CEP are discussed.