A neutron spectroscopy study of magnetic excitations in uranium oxysulphide

Abstract

A neutron spectroscopy experiment has been performed to observe the position of the crystal-field levels in both the paramagnetic and antiferromagnetic phases of UOS. The J-4 ground manifold undergoes an overall splitting of about 100 meV in agreement with the predictions of a crystal-field model used to analyse specific heat data. Above T_N, two main peaks are observed at 74 and 82 meV with a shoulder at about 87 meV. Below T_N there is a redistribution of intensity together with a shift of the peak positions to 76, 84 and 92 meV at T=30 K. The experimental observations are interpreted in the framework of a refined crystal-field model.