Crystal-field splittings in the cubic Heusler alloysHoPd2Sn andErPd2Sn

Neutron inelastic scattering measurements have been taken with triple-axis and time-of-flight techniques to determine the crystal-field levels of the rare-earth ions in the cubic Heusler alloys ${\mathrm{HoPd}}_2$Sn and ${\mathrm{ErPd}}_2$Sn. The observed excitations have been identified as crystal field in origin by their dispersionless character as well as by the temperature and wave-vector dependence of the intensities. Analysis of the data shows that the energies and intensities can be understood on the basis of a crystalline electric field with cubic point symmetry, with Lea, Leask, and Wolf parameters of W=0.0287(4) meV and x=0.3248(8) for ${\mathrm{HoPd}}_2$Sn, and W=-0.0450(4) meV and x=0.3022(6) for ${\mathrm{ErPd}}_2$Sn. These parameters yield the magnetic triplet ${\Gamma }_5^{\mathrm{}\left(1\right)\mathrm{}}$ as the ground state for holmium, with magnetic moments of (±5.49,0)${\mu }_B$, while the erbium ground state is the magnetic quartet ${\Gamma }_8^{\mathrm{}\left(3\right)\mathrm{}}$ with magnetic moments of (±6.31,±1.33)${\mu }_B$. The crystal-field parameters for the other rare-earth elements have also been calculated by scaling to the values determined for ${\mathrm{HoPd}}_2$Sn.