We present bulk property measurements of NpIr, a newly synthesized member of the Np-Ir binary phase diagram, which is isostructural to the non-centrosymmetric pressure-induced ferromagnetic superconductor UIr. Magnetic susceptibility, electronic transport properties at ambient and high pressure, and heat capacity measurements have been performed for temperature T = 0.55 - 300 K, in a range of magnetic fields up to 14 T and under pressures up to 17.3 GPa. These reveal that NpIr is a moderately heavy fermion Kondo system with strong antiferromagnetic interactions, but there is no evidence of any phase transition down to 0.55 K or at the highest pressure achieved. Experimental results are compared with ab initio calculations of the electronic band structure and lattice heat capacity. An extremely low lattice thermal conductivity is predicted for NpIr at temperatures above 300 K.
We present measurements of the magnetic susceptibility, heat capacity and electrical resistivity of Pu$_{1-x}$Lu$_x$Pd$_3$, with $x$=0, 0.1, 0.2, 0.5, 0.8 and 1. PuPd$_3$ is an antiferromagnetic heavy fermion compound with $T_N=24$~K. With increasing Lu doping, both the Kondo and RKKY interaction strengths fall, as judged by the Sommerfeld coefficient $gamma$ and Neel temperature $T_N$. Fits to a crystal field model of the resistivity also support these conclusions. The paramagnetic effective moment $mu_{mathrm{eff}}$ increases with Lu dilution, indicating a decrease in the Kondo screening. In the highly dilute limit, $mu_{mathrm{eff}}$ approaches the value predicted by intermediate coupling calculations. In conjunction with an observed Schottky peak at $sim$60~K in the magnetic heat capacity, corresponding to a crystal field splitting of $sim$12~meV, a mean-field intermediate coupling model with nearest neighbour interactions has been developed.
We have made an extensive study of the magnetic and electrical properties of double-hexagonal closepacked NpPd3 and a range of U(1-x)Np(x)Pd3 compounds with x=0.01, 0.02, 0.05, and 0.50 using magnetization, magnetic susceptibility, electrical resistivity, and heat capacity measurements on polycrystalline samples, performed in the temperature range 2-300 K and in magnetic fields up to 9 T. Two transitions are observed in NpPd3 at T=10 and 30 K. Dilute Np samples (x<0.05) exhibit quadrupolar transitions, with the transition temperatures reduced from those of pure UPd3.
