Magnetic excitations in monodomain ferromagnetic uranium telluride

Neutron-inelastic-scattering experiments have been performed with triple-axis spectrometers at the Institut Laue-Langevin, Grenoble, on a single-domain (field-cooled) crystal of the actinide ferromagnet (${\mathit{T}}_{\mathit{c}}$=104 K) UTe. The excitation at the zone center (Γ) has an anisotropy gap of 3.6 THz. In the direction of the easy axis 〈111〉, we are able to follow the excitation to the zone boundary, where the frequency is ∼9 THz. In the perpendicular direction the excitation rapidly becomes strongly damped. This is the major new finding of our experiments on a single-domain crystal. The excitation is also broader than the resolution function throughout the zone. We have convoluted the instrumental Gaussian resolution function with a Lorentzian function to obtain this broadening quantitatively. A further broad ‘‘continuum’’ of magnetic scattering is also identified at low temperature; this contribution increases rapidly as the temperature is raised. Our measurements suggest that the 5f electrons in UTe strongly hybridize with the conduction electrons.