Estudo de Interações Hiperfinas em Óxidos RCoO3 (R= Gd e Tb) e Filmes Finos de HfO2 por Meio da Técnica de Espectrospia de Correlação Angular Gama- Gama Perturbada / Hyper¯ne Interaction Study in RCoO3 (R = Gd and Tb) and HfO2 thin ¯lm oxides by Perturbed Angular Correlation Technique

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In the present work, the Perturbed Angular Gamma-Gamma Correlation technique (PAC) was used to measure the Electric Field Gradient (EFG) in two oxide systems: RCoO3 (R = Gd, Tb) perovskite oxide and HfO2 in order to study the behavior of the EFG as a function of temperature. Electric quadrupole hyper¯ne interaction measure- ments were carried out using 111In ¡!111 Cd and 181Hf ¡!181 Ta radioactive probe nuclei. The samples were prepared through a chemical route known as Sol-Gel technique and analyzed with x-ray di®raction. Both nuclei were introduced in to the perovskite samples during the chemical procedure. The thin ¯lms were provided by the Laboratory of Hyper¯ne Interactions at the University of 181Hf Lisbon and the probe nuclei was activated by the irradiation of the thin ¯lm in the reactor of IPEN IEA-R1 at an appropriate time regarding the thickness of the ¯lm. The measurements were taken in the temperature range from 4 K to 1560 K. The results for the perovskite oxides measurements show a site-dependence of the EFG with probe-nuclei occupation and a temperature dependence of EFG that can be explained if spins transitions in Co are considered. The results of EFG measurements in the 25 nm thin ¯lm of HfO2 show a second fraction besides that corresponding to bulk.

ASSUNTO(S)

gradiente de campo elétrico correlação angular perturbada óxidos perovskitas e óxido de háfnio interações hiperfinas óxidos perovskitas e óxido de háfnio interações hiperfinas correlação angular perturbada gradiente de campo elétrico

ACESSO AO ARTIGO

Documentos Relacionados