Synthesis and physical properties of the 10.6 K ferromagnet NdIr3

The magnetic, transport, and thermodynamic properties of NdIr3 are reported. Its PuNi3-type crystal structure (space group R-3m), with lattice parameters a=5.3262(1)Å and c=26.2218(3)Å, was confirmed by powder x-ray diffraction. Our measurements indicate that NdIr3 exhibits a previously unreported paramagnetic to ferromagnetic phase transition below TC=10.6K (determined by using the Arrott plot). The magnetic susceptibility obeys the Curie-Weiss law with an effective magnetic moment of μeff=3.63(2) μB/Nd and a paramagnetic Curie temperature θP=5.4(6)K. The heat-capacity anomaly at TC confirms a bulk nature of the transition, though ΔCp=11.7Jmol-1K-1 is lower than expected for J=9/2 and instead close to the J=1/2 system. This suggests that Nd ions are subject to the crystalline electrical field that removes spin degeneracy and leaves the Nd ions in a doublet ground state. Resistivity and heat-capacity measurements reveal an anomaly at around 70 K. The origin of this anomaly is unknown, but the lack of thermal hysteresis suggests that it is a second-order phase transition and may be related to electronic instabilities. The calculated electronic structure is reported.