Anisotropic Properties of Single-Crystalline CeNiGe2

The anisotropic properties of CeNiGe₂ with a layered crystal structure have been studied by measurements of electrical resistivity, magnetic susceptibility and magnetization. It is confirmed that CeNiGe₂ undergoes two-step antiferromagnetic transition at T_N^I = 4 K and T_N^II = 3 K as reported earlier on polycrystalline samples. CeNiGe₂ is found to exhibit highly anisotropic properties with an easy magnetization axis along the longest crystallographic b direction. The magnetization ratio M(H//b)/M(H⊥b) is estimated to be about 15 at 5 T. The in-plane resistivity ρ<INF>⊥^b</INF>(T) shows double maxima typical of that expected when an interplay of crystal-field and Kondo effects plays a role. The low-T maximum at 4 K in ρ<INF>⊥^b</INF>(T) is strongly suppressed with increasing magnetic field. This negative magnetoresistance is a result of the strong reduction of magnetic scattering by the ferromagnetic alignment of Ce magnetic moments.