Spin Fluctuations and Non-Fermi-Liquid Behavior of CeNi_2Ge_2

Neutron scattering shows that non-Fermi-liquid behavior of the heavy-fermion compound CeNi_2Ge_2 is brought about by the development of low-energy spin fluctuations with an energy scale of 0.6 meV. They appear around the antiferromagnetic wave vectors $(1\mathrm{/}21\mathrm{/}20)$ and $(003\mathrm{/}4)$ at low temperatures, and coexist with high-energy spin fluctuations with an energy scale of 4 meV and a modulation vector $(0.23,0.23,1\mathrm{/}2)$. This unusual energy dependent structure of $\text{Im}\chi (\mathit{Q},E)$ in $\mathit{Q}$ space suggests that quasiparticle bands are important.