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 co ntent 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 developmen t 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 prope rties 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 effe ct is seen when Ni is replaced by Cu. Already at 10% Cu the system for ms a spin-glass-like state below 0.9 K. At 20% Cu this behavior is str engthened, but antiferromagnetic order of the type seen in CePtSn or C ePdSn is not reached. The results show further that the change in 4f h ybridization initiated by volume expansion in the alloyed samples is n ot the dominating mechanism strengthening the magnetic correlations. D ecisive is the increase in d electron density when replacing Ni by Cu.