Crystal Fields and Metamagnetism in NdNiPb and Nd$_{5}$NiPb$_{3}$

We report magnetic, transport and thermodynamic measurements for recently-synthesized NdNiPb (orthorhombic TiNiSi-type structure) and Nd$_{5}$NiPb$_{3}$ (hexagonal Hf$_{5}$CuSn$_{3}$-type structure), as well as non-magnetic Y-based analogs. High-temperature Curie-Weiss fits yield effective moments of 3.59 $\mu_{B}$ for NdNiPb and 3.70 $\mu_{B}$ for Nd$_{5}$NiPb$_{3}$. These are close to the Nd$^{3+}$ ionic moment, 3.62 $\mu_{B}$, showing that Ni is nonmagnetic in both cases. For NdNiPb a peak seen in both the magnetization and specific heat at 3.5 K indicates an apparent antiferromagnetic transition at that temperature. Specific heat measurements show this transition to be formed from crystal-field-split Nd magnetic levels, and we have made preliminary estimates of the crystal field scheme. Nd$_{5}$NiPb$_{3}$ exhibits two magnetic transitions, an antiferromagnetic transition at 42 K and an apparently weak ferromagnetic canting transition at 8 K. Entropy measurements also show the ground state to be composed of crystal-field-split doublet of magnetic levels. $M$-$H$ curves show metamagnetism at temperatures between the two magnetic transitions. The materials are metallic, and we will discuss transport results providing a further probe of the magnetic behavior.