mu SR studies on the development of magnetism in the Kondo semimetal CeNiSn caused by doping with La, Cu and Pt

Muon spin-rotation-relaxation (mu SR) experiments were performed at low temperature in transverse, zero and longitudinal field on Ce0.85La0.15NiSn, CePt0.12Ni0.88Sn, CePt0.2Ni0.8Sn and CeCu0.1Ni0.9Sn as an extension of our previous studies of the CeTSn (T = Ni, Pt, Pd) series. In CeNiSn we have proven the formation of weakly dynamic paramagnetic spin correlations, below 1 K which, however, do not lead to long-range magnetic order even at T = 10 mK. For Ce0.85La0.15NiSn the predicted heavy-hole gas antiferromagnetism is not seen, but rather a reduction of magnetic correlations. Both Pt-doped compounds exhibit no significant enhancement of spin correlations although CePtSn is an antiferromagnet with T-N approximate to 7 K. The magnetic correlations increase strongly for CeCu0.1Ni0.9Sn up to the point of forming a spin-glass-like state at T < 0.9 K. Doping with either 20% Pt or 10% Cu increases the unit cell volume by roughly 1%. Volume expansion in CeTSn is a known cause for a reduction of the hybridization between f electron states and conduction electrons, thereby strengthening magnetic interactions. Yet, the marked differences in magnetic behaviour between replacing Ni in part by either isoelectronic Pt or by Cu, which has two more d electrons, indicates that the dominating effect must be the increase of the d electron density instead.