Influence of iron ions on the magnetic properties of CaO–SiO2–P2O5–Na2O–Fe2O3 glass–ceramics

Room temperature Electron Paramagnetic Resonance (EPR) spectra and temperature dependent magnetic susceptibility measurements have been performed on 41CaO.(52−x)SiO2.4P2O5.xFe2O3.3Na2O ( 2 ≤ x ≤ 10 mol % ) glass–ceramics. The parent glass samples were prepared by quenching the homogenized melt from 1550 ∘C. The glasses were then heat-treated at 1050 ∘C for 3 h and slowly cooled to room temperature to yield glass–ceramics. EPR and high temperature magnetic susceptibility measurements were made to elucidate the state of Fe+3 ions in the glass–ceramics. The EPR absorption line centered at g ≈ 4.3 disappeared at higher concentrations of Fe2O3. The intensity and linewidth of the absorption line centered at g ≈ 2.1 increased as the Fe2O3 concentration was increased. Information about the structural changes involving iron ions, their valence state and type of magnetic interactions between the Fe ions was obtained using EPR and magnetic susceptibility measurements. The temperature dependence of the magnetization of the glass–ceramics with low Fe2O3 concentrations exhibit both ferrimagnetic and paramagnetic contributions. The results obtained have been used to understand the structural changes occurring in the vicinity of iron ions and the nature of magnetic interactions between the iron ions in these glass–ceramics.