Influence of Impurity Charge-State on the Temperature Dependence of the Electric-Field Gradient

J. SHITU; A.F. PASQUEVICH; A.G. BIBILONI; M. RENTERÍA; F.G. REQUEJO

MODERN PHYSICS LETTERS B

WORLD SCIENTIFIC PUBL CO PTE LTD

Lugar: London, UK; Año: 1998 vol. 12 p. 281 - 289

0217-9849

We present, for the first time, clear experimental evidence of the influence of the electronic configuration of probe-atoms on the temperature dependence of the electric-field gradient (EFG) tensor at impurity sites. We measured the EFG at 111In→111Cd and 181Hf→ 181Ta impurity sites in a complete series of semiconducting and insulating compounds with the same crystalline structure, using the Perturbed-Angular-Correlation technique. The results of this systematic study show that while the principal component VZZ of the EFG increases with temperature at Cd-impurity sites, it decreases at Ta-impurity sites. This temperature dependence is associated with the redistribution of the electronic charge lack or excess located at the impurity center. A simple model is presented based on charge transfer from the probe to its neighbors, in terms of the acceptor and donor nature of the mentioned impurities.