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

TL;DR

This study employs neutron scattering to identify and analyze the crystal field levels of Pr$^{3+}$ in PrOs$_4$As$_{12}$, revealing the ground state and excited states, and comparing these with PrOs$_4$Sb$_{12}$ to understand their differences.

Contribution

First detailed neutron scattering analysis of Pr$^{3+}$ crystal field levels in PrOs$_4$As$_{12}$, clarifying the ground state and excited states and their differences from PrOs$_4$Sb$_{12}.

Findings

Ground state is a magnetic $ extGamma_4^{(2)}$ triplet.

Excited states at 0.4, 13, and 23 meV.

Differences in ground states explained by microscopic origin.

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 $\Gamma_4^{(2)}$ triplet, and the excited states $\Gamma_1$, $\Gamma_4^{(1)}$ and $\Gamma_{23}$ 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.