Size-dependent dielectric behaviour of magnetic Gd2O3 nanocrystals dispersed in a silica matrix

Magnetic nanocrystalline Gd2O3 particles have been successfully synthesized in a silica glass matrix by the sol - gel method at calcination temperatures of 700 degrees C and above. The optical spectra, corresponding to the transition from ground S-8(7/2) to the excited P-6, I-6 and D-6 multiplets, show a large blue shift which increases with decreasing particle size. Calculated free ion parameters represent different electrostatic and spin - orbit interactions of nanocrystalline Gd2O3 compared with the bulk Gd2O3. The thermal behaviour of magnetization (zero-field-cooled and field-cooled) and magnetic hysteresis of Gd2O3 nanocrystals in the 5 - 300K temperature interval have demonstrated that the Gd2O3 nanocrystals present in these glasses display superparamagnetic - ferromagnetic transition at low temperatures. The present Gd2O3 nanoparticles embedded in the silica glass matrix show a high (similar to 10(3)) dielectric constant with considerable low loss and good temperature-independent character associated with an important technological implication which promises wide applications in memory devices.