Stabilization of the 5f energy band in actinide--Rh3 intermetallic compounds

The magnetic susceptibilities and electrical resistivities of ThRh3, URh3, NpRh3, and PuRh3 have been measured from 2–300°K. These compounds have the cubic AuCu3‐type structure with a total lattice parameter variation of only 0.5% for the latter three compounds. These materials are metallic and have room‐temperature resistivities of about 50 μΩ‐cm. The susceptibility of ThRh3 is temperature‐independent. The URh3 susceptibility decreases weakly with temperature. The susceptibility of NpRh3 has a large 0°K‐value of 5.5 × 10−6 emu/g, decreases as −T2 up to 125°K, and then fits a Curie‐Weiss law with peff = 3.63 μB/NpRh3 and θ =−483°K. PuRh3 is antiferromagnetic below TN = 6.6°K. The resistivities of ThRh3, URh3, and NpRh3 increase from their residual values as ρ = ρo + ATn, where n = 5, 3, and 2, respectively. The PuRh3 resistivity follows ρ = ρo + AT above TN. The data are interpreted by a model in which the 5f level is above the Fermi energy in ThRh3, a broad, hybridized 6d‐5f band overlaps the Fermi level in URh3, NpRh3 is nearly magnetic with a spin fluctuation temperature TS ≃ 5°K, and PuRh3 is weakly magnetic with a moment of about 1 μB subject to spin fluctuations above TN.