Studies of magnetic and dielectric properties on Eu2O3nanoparticles embedded in silica matrix

• Main Authors: Ching-Hsuan Chen, 陳慶軒
• Other Authors: Hung Duen Yang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/65574774150735010987

碩士 === 國立中山大學 === 物理學系研究所 === 98 === Magnetic nanocrystalline Eu2O3 (0.5 mol %) particles have been synthesized in a silica glass matrix by the sol-gel method at calcination temperatures of 700oC and above. X-ray and TEM studies reveal the nanocrystals with mean sizes in the range 4–8 nm, larger in the samples calcined at higher temperatures. The magnetization and magnetic hysteresis of Eu2O3 nanocrystals in the temperature range of 2-300K have demonstrated that the Eu2O3 nanocrystals in these glasses display superparamagnetic state. The temperature dependence of dielectric constant curves demonstrate a broad maximum around Tm ~ 270 K characteristic by diffuse phase transition (DPT). At the highest applied magnetic field 9 tesla, at superparamagnetic phase, the dielectric constant around Tm decreases almost ~ 1.5 (at 2.5 kHz) times compared with that at zero field for the sample calcined at 700℃ (~2 nm). The magnetodielectric effect observed in the glass composite is considered to be affected with the direct consequence of magnetoresistance changes which depends on the magnetic nanoparticle size and separation. Combustion mechanism is closely relate to the thermally activation oxygen vacancy. Such a material might be treated as a potential candidate for device miniaturization.