Ground-state properties and magnetic excitations of the mixed valence state: Cerium-based alloys

Both the static and dynamic magnetic behavior of the mixed valence system, Ce/sub 0.9-x/La/sub x/Th/sub 0.1/, have been studied through magnetic susceptibility and inelastic neutron scattering experiments. For small La concentrations (x< or approx. =0.09), the system exhibits a first-order valence transition to a strongly mixed valent ground state, whereas nearly integral valent, local moment behavior results for x> or approx. =0.4. For the strongly mixed valent system Ce/sub 0.74/Th/sub 0.26/, the inelastic neutron spectra are characterized by a broad quasielastic peak, while for x> or approx. =0.14 in the Ce/sub 0.9-x/La/sub x/Th/sub 0.1/ system, the mixed valence effects are weaker and crystalline electric field excitations begin to appear. This occurs when the spin-fluctuation energies associated with the mixed valent state are smaller than the crystal-field excitation energy. Simple relationships emerge which connect various energy-related parameters, namely, the valence transition temperature, the Fermi liquid susceptibility at T = 0 and the ground-state spin-fluctuation energy as measured in the neutron scattering experiments