Electrical and Magnetic Properties of Some Cubic Intermetallic Compounds of Plutonium with Ru, Rh, Ir, Pd, and Pt

The electrical resistivities and magnetic susceptibilities of the cubic intermetallic compounds of the form $\mathrm{Pu}{X}_2 (X=\mathrm{R}\mathrm{u},\mathrm{R}\mathrm{h},\mathrm{I}\mathrm{r},\mathrm{P}\mathrm{t})$ and $\mathrm{Pu}{X}_3 (X=\mathrm{R}\mathrm{h},\mathrm{P}\mathrm{d},\mathrm{P}\mathrm{t})$ have been measured from 2 to 300 °K. The $\mathrm{Pu}{X}_3$ compounds order antiferromagnetically with Néel temperatures $T_N$ of 6.6, 24, and 40 °K, respectively. The resistivities of the $\mathrm{Pu}{X}_3$ compounds decrease rapidly below $T_N$, and there is also an abrupt change in the slope of the resistivity-versus-temperature curve at $T_N$ in Pu${\mathrm{Rh}}_3$. Pu${\mathrm{Pt}}_2$ orders ferromagnetically at a Curie temperature of $T_C=(6.0\mathrm{}\pm 0.3)$ °K, and the resistivity falls dramatically below $T_C$. Pu${\mathrm{Rh}}_2$ has a temperature-dependent susceptibility but there is no evidence for magnetic order, while the susceptibilites of Pu${\mathrm{Ru}}_2$ and Pu${\mathrm{Ir}}_2$ are temperature independent. However, the resistivities of Pu${\mathrm{Rh}}_2$, Pu${\mathrm{Ru}}_2$, and Pu${\mathrm{Ir}}_2$ have anomalous negative curvature at high temperatures, although the slopes remain positive throughout the temperature range investigated. The results are discussed in terms of the interatomic distance between plutonium atoms and the localized-spin-fluctuation model.