A study of Ni-substitution effects on heavy-fermion CeCu ₂Si ₂-Similarities between Ni substitution and high-pressure effects

The effects of Ni substitution on Ce(Cu _1-xNi _x) ₂Si ₂ have been studied by specific heat and electrical resistivity measurements. The specific heat measurement has revealed that the enhanced quantum fluctuations around an antiferromagnetic quantum critical point are markedly suppressed by Ni substitution, and that the Fermi liquid state recovers in the Ni-rich region (x ≥ 0:12). The characteristic T-linear dependence of the resistivity has been observed at approximately x ̃ 0:10 together with a sign of superconductivity. The variation of n in the form of ρ - ρ0 = aT ⁿ against T ^max ₁ , at which the resistivity peaks, coincides with the case of high-pressure experiments on pure CeCu ₂Si ₂. The anomalous T-linear behavior appears to occur in the crossover region from the Kondo regime to the valence fluctuation regime rather than in the conventional antiferromagnetic quantum critical region.