Crystal field effects in CeOs₄Sb₁₂ as determined by inelastic neutron scattering

The ground state and physical properties of CeOs₄Sb₁₂ are primary determined by the competition among three types of energies which are all related to interactions of the Ce³⁺ 4f electron with the lattice and the spin lattice, i.e., the Kondo interaction, the Ruderman-Kittel-Kasuya-Yosida interaction, and the crystal field energy. In this work, inelastic neutron scattering experiments were performed on CeOs ₄Sb₁₂ powder samples at low temperatures in order to investigate the magnetic interactions, the origin of unusual physical properties and, in particular, to elucidate the ground state of crystal field splitting. The result indicates that, within the accuracy of experimental error, no well defined crystal field effect could be detected around the expected energy of 28.2 meV as computed on the basis of a localized Ce³⁺ state model. That means that other causes are responsible for the deviation of inverse susceptibility from the linear Curie law at low temperatures and that further studies are necessary to understand the anomalous transport properties of CeOs₄Sb₁₂.