Ferromagnetic-like behavior in nanosilica glass containing iron ions and giant magnetodielectric effect in composites of these glasses with mesoporous silica

Abstract

Iron ion containing nanodimensional silica glass was grown within the 5 nm pores of mesoporous silica. The nanocomposite material showed ferromagnetic-like behavior at room temperature. This was ascribed to the presence of Fe²⁺ and Fe³⁺ ions within the nanodimensional glass phase and an antiferromagnetic superexchange interaction between them. The nanocomposite showed a large magnetodielectric coefficient (up to 51%) for a magnetic field of 1.7 T. The dielectric loss (tan δ) was found to be in the range 0.35 to 0.66. This was explained on the basis of Catalan’s model of space–charge polarization. From the theoretical fitting of experimental data, magnetoresistance of nanoglass phase was extracted to be 58% up to a magnetic field of 1.7 T.