Study of weak magnetism effects in heavy-electron systems by μ+SR (abstract)

Abstract

We will present results from μ+SR investigations of the heavy-electron systems CeAl3, U2Zn17, UCu5, and UCd11. The latter three are known to order antiferromagnetically at low temperatures. The transition into the antiferromagnetic phase is clearly manifest in the μ+SR data, but also above the Néel temperatures some weak magnetism seems to persist as can be inferred from enhanced μ+ relaxation rates even in zero applied field. The involved effective moments are much reduced in comparison to the free-ion f moments, generally below 0.5 μB, and the magnetic order may be of the spin-glass or spin-density wave type. In nonmagnetic CeAl3 a spontaneous μ+ precession signal appears below 0.7 K in zero external field which implies the presence of even some coherent magnetic order of probably very short range in this system. These findings are consistent with other recent μ+SR and neutron scattering work, indicating that weak magnetic mechanisms seem to be a characteristic feature of heavy-electron systems.