Transport properties of CoSb/sub 3/ doped with magnetic impurities Fe and Ni

Abstract

Effects of doping with magnetic impurities (Fe and Ni) on the thermal conductivity of CoSb/sub 3/ have been investigated to make clear the origin of the scattering of phonons by magnetic ions. Samples with different impurity concentration x=3, 5, and 10 at.% were prepared by hot pressing. The effects of doping on the electronic transport properties are explained in terms of a Kane model, in agreement with a result of the band calculation. Our analysis of the magnetic susceptibility on the basis of the crystal field theory suggests that the magnetic ions in CoSb, have trivalent paramagnetic states (mainly Fe/sup 3+/ S=5/2 and Ni/sup 3+/ S=1/2). The lattice thermal conductivity /spl kappa/L decreases to about 0.04 Wcm/sup -1/ K/sup -1/ with increasing x. The consideration of the electronic states of Fe and Ni in CoSb, and the theoretical calculations of /spl kappa/L based on the Debye model lead to a conclusion that the magnetic Fe and Ni ions probably ad as strong scattering centers of phonons (a model proposed by Slack and Galginaitis) and play an important role in reducing the lattice thermal conductivity of not only CoSb/sub 3/ but also filled skutterudites.