The influence of impurities and alloying in the Kondo semimetal CeNiSn as seen by mu SR

The temperature dependence of the muon spin relaxation rate lambda was measured in two samples of CeNiSn with markedly different impurity content and in the quasi-ternary compounds CePtxNi1-xSn (x = 0.12, 0.2) and CeCuxNi1-xSn (x = 0.05, 0.1, 0.2) in order to study the development of magnetic correlations. No significant change in lambda was found for the two samples of CeNiSn although their low temperature specific heat differs strongly. Hence mu SR probes the intrinsic magnetic properties of the spin-liquid state of CeNiSn. Replacing Ni with up to 20% Pt results only in minor changes of lambda. In contrast, a strong effect is seen when Ni is replaced by Cu. Already at 10% Cu the system forms a spin-glass-like state below 0.9 K. At 20% Cu this behavior is strengthened, but antiferromagnetic order of the type seen in CePtSn or CePdSn is not reached. The results show further that the change in 4f hybridization initiated by volume expansion in the alloyed samples is not the dominating mechanism strengthening the magnetic correlations. Decisive is the increase in d electron density when replacing Ni by Cu.