Multiferroic properties of Bi_0.8Dy_0.2-xLa _xFeO₃ nanoparticles

Bi_0.8Dy_0.2-xLa_xFeO₃ (BDLFO _x) (x = 0, 0.10 and 0.20 respectively) nanoparticles were prepared by the ethylene glycol based sol-gel method. The influence of the average radius and the effective magnetic moment of Bi-site ion on the structure, magnetic and dielectric properties, and the effective magnetic susceptibility of BDLFO _x nanoparticles was investigated. All the samples were indexed to the orthorhombic structure based on the results of x-ray diffraction. The grain size of the samples increased with the increase in Bi-site ionic average radius. The magnetization of the samples was found to decrease with the effective magnetic moment of Bi-site ion decreasing. The dielectric constant and loss were improved when the Bi-site ionic average radius decreased and the effective magnetic moment of the Bi-site ions increased. The enhanced magnetization M and the polarization P in nanoparticles made the effective magnetic susceptibility of the samples greatly enhanced, in particular for the sample of x = 0. Therefore we concluded that the small amount of substitution of Bi³⁺ ions by trivalent rare-earth ions with a smaller ionic radius than Bi ³⁺ ion and a high magnetic moment in the nano-system was a way to improve the multiferroic properties of BiFeO₃.