A comparative study of the magnetic heavy-electron materials U2Zn17 and UCu5 by μ+SR

A systematic μ+SR study of the magnetic heavy-electron systems U2Zn17 and UCu5 in the paramagnetic and in the magnetically ordered state is presented. In both systems the antiferromagnetic nature of the low-temperature phase could be at least partially confirmed, but the muon reveals significant differences with regard to the phase transition itself. UCu5 behaves like a model-antiferromagnet showing a drastic increase of the relaxation rate both below and above TN, two spontaneous frequencies in the ordered phase, and a Knight shift above TN which scales with the bulk susceptibility. In contrast U2Zn17 shows a loss of μ+ asymmetry by 20% below TN, which is independent of the external field but can be quenched in sufficiently strong longitudinal fields. No scaling of the knight shift and the susceptibility was observed and no critical increase of the relaxation rate λ. Most astonishing is the strong and nonlinear field dependence of λ above and below TN in both compounds. The absence of longitudinal relaxation demonstrates the static origin of λ. (orig.)