Study of the Magnetic Properties of the Actinide Metals: Th1−xUxPd3

Abstract

ThPd₃, with UPd₃, forms a continuous series of solid solutions. These two intermetallic compounds have the hexagonal DO₂₄ structure. We have studied the magnetic susceptibilities of eleven Th_1−xU_xPd₃ alloys (0≤x≤1) at temperatures from 1.4° to 300°K in fields up to 15 kOe and at 4.2°K in fields up to 80 kOe. ThPd₃ is diamagnetic and shows a temperature‐independent susceptibility, but the addition of U, even in small amounts, gives rise to a strongly temperature‐dependent paramagnetic susceptibility. The data analyzed in terms of T against 1/χ−χ_∞ gives a Curie‐Weiss behavior in the high‐temperature region with 3.35 μ_B/U atom at low U concentrations; decreasing to 2.6 μ_B for UPd₃. It appears that the U‐5f electrons form a localized moment for low U concentrations. A deviation from a Curie law at around 100°K for all U concentrations is suggested to be due either to crystal field splitting of the U‐5f levels or to the presence of a narrow 5f band. The lack of any indication of an antiferromagnetic transition in the temperature behavior of the susceptibility at high U concentrations and the linearity of the magnetic moment with magnetic field up to 80 kOe for the same alloys, favors the formation of a very narrow 5f band as the U concentration increases and lends support to previous EPR experiments of Gd in UPd₃, where a similar conclusion was reached.