Localized Correlations in Narrow Conduction Bands. II

Abstract

The problem of a magnetic impurity in a narrow conduction band is studied using doubletime Green's functions. We have used a Wolff model in which a repulsive Coulomb interaction of strength $U$ is limited to the impurity site. The coupling of the impurity site to its neighbors because of the kinetic energy is reduced by a scale factor relative to the coupling of host atoms to their neighbors. The difference in the one-electron potential between host and impurity sites is also taken into account. We have solved the decoupled Green's-function equations in the infinite-$U$ limit in the presence of a finite magnetic field. From this solution, a conserving calculation of the zero-field magnetic susceptibility $\ensuremath{\chi}$ is performed and numerical results obtained. We find that for a sufficiently weak coupling between the impurity atom and its neighbors, a Curie-law behavior of $\ensuremath{\chi}$ can be obtained over the four decades of temperature studied. Evidence of Kondo saturation of $\ensuremath{\chi}$ is found for more strongly coupled impurities. The susceptibility shows no evidence of singular behavior at zero temperature.