An extensive experimental study by magnetic-resistivity, magnetostriction, and thermal-expansion measurements on a single crystal of the hexagonal ${\mathrm{PrNi}}_5$ compound is presented. The magnetoelastic results are quite satisfactorily interpreted within a model involving the crystal-field and quadrupolar interactions acting on the Pr ions and taking into account the Ni contribution. All the unusual features, especially the maxima observed around 15 K in the thermal variations of these properties, arise from crystal-field effects which lead to a nonmagnetic singlet ground state lying about 40 K below the first magnetic level. The induced Ni magnetism, although very small, strongly influences the observed behavior, especially the high-temperature magnetic susceptibility. The magnetoelastic coefficients $B^{\alpha 1}$ and $B^{\alpha 2}$ and the total quadrupolar coefficients $G^{\alpha }$ and $G^{\epsilon }$ were determined, leading to the experimental evidence of antiferroquadrupolar interactions between rare-earth ions in ${\mathrm{PrNi}}_5$.

• Received 29 June 1987

DOI:https://doi.org/10.1103/PhysRevB.37.1733