Estudo das propriedades físicas de sistemas multiferróicos baseados em Ferrita de Bismuto

Abstract

The physical properties of the rare-earth modified BiFeO3 (BFO) multiferroic system have been investigated, considering the substitution of the bismuth ion placed in the A site of the perovskita structure. The influence of the rare-earth content on the structural and microstructural properties were taken into account. The obtained results suggest that the smaller rare-earth doping ion (Gd) tend to occupy the B site of the perovskite structure, revealing thus its amphoteric character. Through the investigation of the dielectric properties, performed on cryogenic temperatures, it was also possible to identify a low temperature dielectric anomaly, which has been related to both the double- and super-exchanges interactions mechanisms, related to the magnetic component of the ferrite BFO samples. This result was obtained from the activation energies values. On the other hand, the ionic radius dependence of the activation energy has shown that the Gd ion strongly affected the defect mechanisms through oxygen vacancies, which confirm the amphoteric characteristics of the Gd ion. This result, which has not been reported up today, is very important from broth fundamental and the technological point, leading to new perspectives for practical applications since the involved physical parameter could be optimized by doping with amphoteric ions, as well as to promote the substitution of hardazous and heavy chemical elements, in orther to preserve the environment.