Neutron-scattering studies on CeM2Ge2(M=Ag, Au, and Ru)

The results of elastic, quasielastic, and inelastic neutron-scattering studies on polycrystalline Ce${\mathit{M}}_2$ ${\mathrm{Ge}}_2$ (M=Ag, Au, and Ru) are presented. All compounds reveal long-range magnetic order at low temperatures. Ferromagnetic (M=Ru), antiferromagnetic (M=Au), and incommensurate (M=Ag) structures were detected. Using time-of-flight (TOF) techniques, the crystalline electric-field splittings were determined. With high-resolution TOF experiments the temperature and wave-vector dependence of the magnetic relaxation rate was studied. Korringa-like behavior was found for the Au and Ru compounds. In ${\mathrm{CeAg}}_2$ ${\mathrm{Ge}}_2$ the temperature dependence of the magnetic relaxation rate exhibits a square-root dependence at high temperatures and shows a residual linewidth for low T. This behavior can be explained by strong hybridization effects of the f electrons with the delocalized band states which are active in heavy fermion systems. Previous results in ${\mathrm{CeCu}}_2$ ${\mathrm{Ge}}_2$ and ${\mathrm{CeNi}}_2$ ${\mathrm{Ge}}_2$ are included, whenever necessary. Detailed comparison is made with results obtained in the disilicides.