  Neutron scattering shows that non-Fermi-liquid behavior of the heavy-Fermion
compound CeNi_2Ge_2 is brought about by development of low-energy spin
fluctuations with an energy scale of 0.6 meV. They appear around
antiferromagnetic wave vectors $({1/2} {1/2} 0)$ and $(0 0 {3/4})$ at low
temperatures, and coexist with high-energy spin fluctuations with an energy
scale of 4 meV and a modulation vector $(0.23, 0.23, {1/2})$. The energy
dependence of the spin fluctuations is a peculiar character of CeNi_2Ge_2 which
differs from typical heavy-Fermion compounds, and suggests importance of
low-energy structures of quasiparticle bands.
