Structural characterization and magnetic properties of iron-phosphate glass prepared by sol-gel method

The relationship between the local structure and magnetic properties of iron phosphate glass xFe2O3 • (100-x) P2O5 abbreviated as xFeP prepared by a sol-gel method has been investigated. From the Mössbauer spectroscopy results, it was found that iron ions are present in FeIII(distorted octahedral) and FeII(octahedral) coordination. HAADF-STEM images and elemental mapping results revealed that iron and phosphorus are uniformly dispersed in the system. It is clear from the magnetic susceptibility results that only 50FeP glass heat-treated at 200°C shows spin glass behavior and all other glasses are superparamagnetic at low temperatures. The Weiss temperatures (θw) obtained for all the glasses were negative, suggesting that the interaction between the magnetic moments is antiferromagnetic. In these samples, the higher the proportion of FeIII ions, the higher the frustration of the entire system is. The [FeIII] / [Fetotal] molar ratio decreases as the heat-treatment temperature increased.