Spin fluctuation and crystal field excitation of heavy-fermion compound YbAgGe studied by inelastic neutron scattering

An inelastic neutron scattering experiment has been performed on a new heavy-fermion compound, YbAgGe, for a polycrystalline sample at zero magnetic field. A quasielastic scattering and a crystal field excitation at 12 meV are observed. Both are broadened due to the Kondo effect with an intrinsic width of 0.9 meV at 1.5 K, which increases to about 3 meV at 300 K. The temperature dependence follows Γ₀ + A√T typically observed in Kondo systems. Crystal field parameters are also deduced. To explain the result that only one excitation is observed at 12 meV, the B₂₂ term is assumed as the main component.