Inelastic neutron scattering studies of Crystal Field Levels in PrOs${}_4$As${}_{12}$

Abstract

We use neutron scattering to study the Pr${}^{3+}$ crystalline electric field (CEF) excitations in the filled skutterudite PrOs${}_4$As${}_{12}$. By comparing the observed levels and their strengths under neutron excitation with the theoretical spectrum and neutron excitation intensities, we identify the Pr${}^{3+}$ CEF levels, and show that the ground state is a magnetic $\hat{I}{“}_4^{(2)}$ triplet, and the excited states $\hat{I}{“}_1$, $\hat{I}{“}_4^{(1)}$ and $\hat{I}{“}_{23}$ are at 0.4, 13 and 23 meV, respectively. A comparison of the observed CEF levels in PrOs${}_4$As${}_{12}$ with the heavy fermion superconductor PrOs${}_4$Sb${}_{12}$ reveals the microscopic origin of the differences in the ground states of these two filled skutterudites.

7 pages, 7 figures