Inelastic Neutron Scattering Study Of Crystal Field Levels In Pros4as12

We use neutron scattering to study the Pr3+ crystalline electric field (CEF) excitations in the filled skutterudite PrOs4As12. By comparing the observed levels and their strengths under neutron excitation with the theoretical spectrum and neutron excitation intensities, we identify the Pr3+ CEF levels and show that the ground state is a magnetic Gamma((2))(4) triplet, and the excited states Gamma(1), Gamma((1))(4), and Gamma(23) are at 0.4, 13, and 23 meV, respectively. A comparison of the observed CEF levels in PrOs4As12 with the heavy fermion superconductor PrOs4Sb12 reveals the microscopic origin of the differences in the ground states of these two filled skutterudites.