Synthesis and physical properties of the 10.6 K ferromagnetNdIr3

Abstract

The magnetic, transport, and thermodynamic properties of $\mathrm{Nd}{\mathrm{Ir}}_{3}$ are reported. Its $\mathrm{PuN}{\mathrm{i}}_{3}$-type crystal structure (space group $R\ensuremath{-}3m$), with lattice parameters $a=5.3262(1)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=26.2218(3)\phantom{\rule{0.16em}{0ex}}\AA{}$, was confirmed by powder x-ray diffraction. Our measurements indicate that $\mathrm{Nd}{\mathrm{Ir}}_{3}$ exhibits a previously unreported paramagnetic to ferromagnetic phase transition below ${T}_{C}=10.6\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ (determined by using the Arrott plot). The magnetic susceptibility obeys the Curie-Weiss law with an effective magnetic moment of ${\ensuremath{\mu}}_{\mathrm{eff}}=3.63(2) {\ensuremath{\mu}}_{B}/\mathrm{Nd}$ and a paramagnetic Curie temperature ${\ensuremath{\theta}}_{P}=5.4(6)\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The heat-capacity anomaly at ${T}_{C}$ confirms a bulk nature of the transition, though $\mathrm{\ensuremath{\Delta}}{C}_{p}=11.7\phantom{\rule{0.16em}{0ex}}\mathrm{J}\phantom{\rule{0.16em}{0ex}}\mathrm{mo}{\mathrm{l}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ 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.