Colossal dielectric and magnetodielectric effect inEr2O3nanoparticles embedded in aSiO2glass matrix

Abstract

An intriguing colossal enhancement of dielectric constant along with magnetodielectric (MD) behavior is observed in nanoparticle (NP) ${\text{Er}}_{2}{\text{O}}_{3}$ $(0.5\text{ }\text{mol}\text{ }\mathrm{%})$ embedded ${\text{SiO}}_{2}$ glass matrix synthesized via sol-gel route. A broad dielectric peak with a maximum at ${T}_{m}$ $(\ensuremath{\sim}270\text{ }\text{K})$ exhibits typical diffuse phase transition following modified Curie-Weiss behavior. Conduction mechanism (showing energy barrier ${E}_{a}\ensuremath{\sim}1.13\text{ }\text{eV}$ near ${T}_{m}$) is closely related to the thermally activated oxygen vacancies. At the highest applied magnetic field 9 T, the dielectric constant around ${T}_{m}$ is enhanced almost $\ensuremath{\sim}2.75$ (at 2.5 kHz frequency) times compared with that at zero field. The MD effect observed in this glassy composite is considered to be associated with the direct consequence of magnetoresistance changes which depends on the magnetic NP size and separation.