Neutron scattering studies of the paramagnetic response in the mixed-valence alloy ${\mathrm{Ce}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Th}}_{\mathrm{x}}$ at high energy

We report on the inelastic neutron scattering investigations of the cerium γ⇆α valence transition in ${\mathrm{Ce}}_{0.74}$ ${\mathrm{Th}}_{0.26}$ at energy transfers up to ∼500 meV. The paramagnetic response across the transition was studied in detail at five temperatures between 10 and 200 K. The obtained magnetic scattering functions consist of a broad peak with a line shape consistent with a generalized relaxational spin dynamics. As the temperature decreases across the transition the magnetic intensity drops sharply, accompanied by an abrupt broadening of the linewidth corresponding to a spin-fluctuation energy much higher than the thermal energy. Within experimental precision, we find no evidence of additional inelastic peaks due to crystal-field excitations. The static single-site susceptibility obtained by a Kramers-Kronig analysis agrees well with the bulk susceptibility. The comparison of the present results with analysis in terms of a ‘‘dense impurity’’ model of the f electron in hybridization with the conduction-band states is discussed.