Large magnetodielectric effect in composites of Fe2O3·SiO2nanoglass and mesoporous silica

Abstract

Composites of Fe2O3·SiO2 nanoglasses and mesoporous silica having a pore diameter of 5.5 nm were synthesized using hydrothermal and sol gel methods. The samples exhibited ferromagnetic behaviour which was the result of antiferromagnetic interaction between Fe2+ and Fe3+ ions in the nanoglass. The nanocomposites showed rather large values of magnetodielectric parameter, the range being 7.9%–51.19% depending on the nanoglass composition and the measuring frequency. The experimental data were satisfactorily fitted to Catalan's model substantiating the fact that the dielectric permittivity changes were caused by the Maxwell–Wagner space charge polarization arising at the interfaces of the mesoporous silica and the iron-containing Nanosilica glass phase. Also, there were substantial changes in magnetoresistance (in the range 16.79%–33.47%) up to an applied magnetic field of 15 kOe. The large magnetodielectric effect observed in these nanocomposites makes them suitable for application as magnetic sensors.