Effect of chemical pressure on physical properties of antiferromagnetic Kondo lattice Ce2Ni3Ge5

We have studied the enhancement of Kondo scattering in the heavy fermion compounds Ce2Ni3Ge1-xSix5 by measuring electrical resistivity ρ(T), magnetic susceptibility χ(T), isothermal magnetization M(B), specific heat CP(T) and magnetoresistance. All the members of this series crystallize in U2Co3Si5-type orthorhombic structure with space group Ibam. Magnetic susceptibility and specific heat data show that two step antiferromagnetic transitions at x = 0 reduce to a single transition at x = 0.15 followed by a complete suppression of antiferromagnetic ordering at x = 0.20. Positive magnetoresistance below the transition temperature confirms that the transitions are antiferromagnetic up to x = 0.15 and the negative magnetoresistance in the paramagnetic region implies the freezing out of spin-flip scattering in Kondo compounds under the application of magnetic field. Kondo temperature, estimated from paramagnetic Curie temperature and magnetoresistance data, increases with increasing x in Ce2Ni3Ge1-xSix5 for x⩽0.80. The γ values also indicate that the Kondo temperature enhances with increasing x after the suppression of antiferromagnetic ordering. Maximum γ value (∼76 mJ mol−1 K−2 Ce−1) is observed at x = 0.20 which indicates that the heavy fermion behavior is more pronounced at the magnetic-nonmagnetic boundary. A significant resistivity increase at a particular magnetic field is observed for T = 3.5 K, 3.8 K and 4 K (x = 0 sample) and it is observed for T = 3 K (x = 0.15 sample).