PAC STUDIES OF AG-HF INTERMETALLIC COMPOUNDS

The hyperfine quadrupole interaction of Ta-181 and Cd-111 probes in Hf Ag and Hf2Ag compounds was studied at 24 to 1100 K with the time -diff erential perturbed angular correlation (TDPAC) technique. The EFGs mea sured in HfAg on Ta-181 and Cd-111 are 1.388(5)x10(18) Vcm(-2) and 0.3 40(5)x10(18) Vcm(-2), respectively. For both probe atoms a linear decr ease of the EFG with temperature was observed with slopes 1.11(2)x10(- 4) K-1 and 1.73(5)x10(-4) K-1 for Ta-181 and Cd-111, respectively. In Hf2Ag, 0.469(2)x10(18) Vcm(-2) was determined on Ta-181 nuclei and 0.4 28(5)x10(18) Vcm(-2) on Cd-111. Also a linear EFG temperature dependen ce with the large slope of 2.39(6)x10(-4) K-1 was observed for Cd-111 probes in Hf2Ag, while the EFG measured on Ta-181 nuclei in this compo und exhibits a very weak temperature variation which can be fitted nei ther with a linear T nor a T-3/2 dependence. In all cases the electron ic contributions to the EFG are very small indicating that these trans ition element systems do not obey the universal correlation between th e electronic and the ionic EFG observed in numerous other systems not belonging to the transition metal series.