Muon spin relaxation studies of magnetic order in Y1-xUxPd3 and UPd4

We have performed muon spin relaxation (μSR) measurements of polycrystalline specimens of Y1-xUxPd3 with x=0.1, 0.2, 0.4, and UPd4. We demonstrate that UPd4 and Y0.6U0.4Pd3 exhibit spin glass order, while the predominant volume fraction remains nonmagnetic at T→0 in Y0.8U0.2Pd3 and the muon spin relaxation rate becomes even smaller in Y0.9U0.1Pd3, indicating the disappearance of magnetic order with decreasing U concentration x. These results are discussed in terms of the competition between the crystalline electric field splitting ΔCEF and the exchange coupling J.