MUON SPIN RELAXATION STUDIES OF MAGNETIC ORDER IN Y1-XUXPD3 AND UPD4

We have performed muon spin relaxation (muSR) measurements of polycrys talline specimens of Y1-xUxPd3 with x=0.1, 0.2, 0.4 and UPd4. We demon strate that UPd4 and Y0.6U0.4Pd3 exhibit spin glass order, while the p redominant volume fraction remains nonmagnetic at T --> 0 in Y0.8U0.2P d3 and the muon spin relaxation rate becomes even smaller in Y0.9U0.1P d3, indicating the disappearance of magnetic order with decreasing U c oncentration x. These results are discussed in terms of the competitio n between the crystalline electric field splitting DELTA(CEF) and the exchange coupling J.