Resistance Anomaly in Palladium-Silver Alloys Containing Rare Earth Impurities

Abstract

Electrical resistivities of Pd and three Pd–Ag alloys (Pd0.5Ag0.5, Pd0.35Ag0.65, and Pd0.25Ag0.75) containing small amounts of Gd and Nd have been determined at temperatures between 1.2° and 40°K. All lanthanidedoped alloys were observed to have resistance anomalies which were similar in character for the heavy and light rare earth solutes. However, the anomalies were found to vary drastically with the host lattice. With decreasing temperature, the resistivity-temperature curves show (1) a sudden increase in slope in the matrix of Pd, (2) a minimum in Pd0.5Ag0.5, and (3) a minimum and a maximum in Pd0.35Ag0.65 and Pd0.25Ag0.75. The present alloys, which constitute a continuous series of solid solutions having a common magnetic impurity, have thus exhibited a gradual shift from one to another of the three possible types of anomalous resistance behavior predicted for dilute magnetic alloys by Kondo and other workers. The shift signifies that a dominant role is played by the host lattice in the mechanism leading to a resistance anomaly. The difficulties in reconciling the present results with predictions on the Kondo theory as related to the sign of the effective s-f exchange integral and earlier EPR measurements are discussed.