Sol-gel synthesis and dilute magnetism of nano MgO powder doped with Fe

Mg oxides doped with 1 % ⁵⁷Fe were prepared by a sol-gel method, and annealed at various temperatures. Nano-size Mg oxides were characterized by Mössbauer spectrometry, magnetization and XRD measurements. The crystalline size of MgO increases with increase of annealing temperature. Samples annealed at 600 °C and 800 °C gave only doublet peaks of paramagnetic Fe³⁺ in Mössbauer spectra although Fe³⁺ doping into MgO induced a distorted structure and showed weak ferromagnetism. It is considered that the magnetic property is due to defect induced magnetism by doping Fe³⁺ into MgO. For a sample heated at 1000 °C, it is found from low temperature Mössbauer spectra that Fe³⁺ species are located at the core and shell of fine MgFe₂O₄ grains and diluted in MgO matrix.