NEUTRON-SCATTERING STUDY OF THE QUADRUPOLAR KONDO ALLOY Y0.8U0.2PD3

Inelastic neutron scattering measurements have been performed on a polycrystalline specimen of Y0.8U0.2Pd3 and on the nonmagnetic analog compound Y0.8Th0.2Pd3 using unpolarized neutrons. The magnetic contribution to the inelastic spectrum at T = 10 K exhibits two distinct peaks centered at energies E almost-equal-to 5 meV and 16 meV, attributed to broadened crystalline electric field (CEF) levels, with half widths at half maximum of approximately 3 meV and approximately 8 meV, respectively. The integrated intensities are consistent with GAMMA5 and GAMMA4 first and second excited state triplets lying above a GAMMA3 doublet ground state for tetravalent U ions in a cubic CEF. The absence of a pronounced low-energy (less-than-or-equal-to 4 meV almost-equal-to k(B)T(K)) quasielastic response provides further evidence that the nonmagnetic GAMMA3 doublet lies lowest in energy. These observations support the interpretation of the thermal, magnetic and transport properties in terms of the two-channel quadrupolar Kondo effect.