Pu neutron scattering studies – Magnetism and structure

Neutron scattering results are presented on δ-phase Pu stabilized with 2% Ga performed on the time-of-flight instrument Pharos in zero magnetic field and also in an 8 T applied field over the temperature range from room temperature down to 1.7 K. Comparison of the field and temperature dependence of the diffraction patterns showed no evidence of peaks of magnetic origin, and thus no long-range order is induced even in an 8 T applied field. Due to the wave-vector character of the scattering, this result can not be explained by the possible cancellation of the orbital and spin components of the moment. Additional inelastic scattering experiments at room temperature did reveal a very weak inelastic feature at 90 meV which is tempting to ascribe to H impurities. However, the feature did not have the expected Q2 intensity dependence as would be expected for H vibrations, and thus the origin of this 90 meV peak is unexplained.