NMR studies of U0.2Y0.8Pd3 and YPd3 at low temperatures

We report results of ⁸⁹Y-NMR measurements on U_0.2Y_0.8Pd₃ as well as YPd₃, performed at frequencies between 9 and 16MHz and at temperatures between 0.25 and 2 K. In this temperature range the average Knight shift is +0.5%, temperature-independent and the same for both materials. Also the NMR linewidth for both compounds was found to be temperature and field independent but one order of magnitude larger for U_0.2Y_0.8Pd₃ than for YPd₃. For U_0.2Y_0.8Pd₃ our results indicate a distribution of internal static fields at the Y sites and a small temperature-dependent enhancement of the spin-lattice relaxation rate T ₁ ^?1 with respect to YPd₃. The NMR spectra are consistent with the presence of very small frozen U moments, but the temperature dependence of the spin-lattice relaxation rate indicates a more complicated situation. In particular (T₁T)^?1 shows an anomalous temperature dependence.