Rare-Earth—Conduction Electron Interaction in 4d and 5d Laves Phases Compounds

Abstract

A systematic investigation has been made of the sign and magnitude of the g shifts of Gd impurities in the AB2 intermetallic Laves phase compounds. Gd was partially substituted in the A site for the elements Sc, Y, La, Th, U, and Zr. The B sites are occupied by elements of the 4d and 5d group whose positions in the periodic table are such as to correspond to an almost filled d band (e.g., Ru, Os, and Rh). Negative Gd g shifts, Δg, up to 7% were observed; the highest was that found in LaRu2. It was found that the closer a B element was to having a filled d shell the larger was the g value. It appears, in keeping with our previous EPR measurements on Gd in Rh-Pd, Pd-Ag alloys and in Cu5Ca intermetallic compounds, that without exception the g shifts are negative when the d band is nearly filled in the host alloy and that the g value has a minimum as a function of the atomic position in the host d band metal. In very fine powders of the hard superconductors (Ce0.99Gd0.01) Ru2 and (Th0.99Gd0.01) Ru2 no change in the Gd g shift was observed in going from the normal to the superconductor state. For the superconductor (La0.15Ce0.85) Ru2 the La Knight shift was also observed not to change in going from well above to well below the superconducting transition temperature. In both experiments Ho≪the upper critical field.