Conduction-electron polarization in rare earth-platinum alloys

Abstract

Nuclear magnetic resonance studies of ¹⁹⁵Pt in the rare-earth-platinum intermetallic compounds of the composition RPt₂ and RPt₅ (R=La, Ce, Pr, and Nd) have been made in the temperature range 80° to 300°K. They have the cubic (MgCu₂ type) and the hexagonal (CaCu₅ type) Laves structures, respectively. In RPt₅ componuds, there are two inequivalent platinum sites and correspondingly, two ¹⁹⁵Pt resonances are observed in each compound. The platinum Knight shifts which are positive, are strongly temperature dependent in all but the lanthanum compounds. The magnetic susceptibilities have been measured in the same temperature range. The Knight shift (K) versus susceptibility curves are straight lines, intersecting the K axis at K₀, corresponding to the lanthanum compounds. The EPR of Gd³⁺ in GdPt₂ has been observed and a g value of 1.8735 has been obtained. The paramagnetic Curie temperatures are positive for RPt₂ compounds and negative for the others. The results have been discussed in terms of the RKKY theory and the Anderson-Clogston mixing. Values of J(0) have been obtained for the two sets of intermetallic compounds.