Antiferromagnetic Kondo lattice to intermediate valence transition in Ce(Au_1-xNi_x)₂Si₂ (0 ≤ x ≤ 1)

Transition effects from magnetically ordered Kondo lattice (KL) behaviour in CeAu₂Si₂ to intermediate valence (IV) behaviour in CeNi₂Si₂ have been investigated by substitution of Au with Ni. These investigations were done through measurements of the lattice parameters, electrical resistivity (ρ(T)), magnetisation (M(^μ0H)) and magnetic susceptibility (χ(T)) on the Ce(Au_1-xNi_x)₂Si₂ (0≤x≤1) series. Lattice parameters as derived from XRD measurements deviate from Vegard's rule around x=0.6-0.8. ρ(T) data indicate KL behaviour in the presence of a crystal field for x≤0.6, the occurrence of magnetic ordering for x≤0.2 and valence fluctuation for x ≤0.8. χ(T) data at high temperatures, follow the Curie-Weiss relation for alloys in the concentration 0≤x≤0.6 (KL region) and give effective magnetic moment values μ_eff close to that expected for free Ce³⁺ ion. The low temperature χ(T) data indicate the onset of antiferromagnetic ordering for x≤0.2. For alloys in the concentration range 0.8≤x≤1, the χ(T) behaviour is reminiscent of intermediate valence (IV) systems. M(;bsup0;esup&H) measurements indicate metamagnetic behaviour for alloys in the concentration range 0≤x≤0.1.