Magnetic Excitations in Uranium Antimonide

Abstract
We report the first observation by neutron inelastic scattering of a collective elementary excitation in a metallic actinide compound. The excitation is longitudinally polarized with respect to the direction of the magnetic moment, has a dispersion of 6.7 THz Å, and has a most unusual temperature dependence. Present models for the electronic structure of this and similar materials are inadequate to account for the dynamical behavior we have observed.