Dilute magnetic properties of Fe doped Al2O3 powders prepared by sol-gel method

Aluminium oxides doped with 1% 57Fe were prepared by sol-gel method, and annealed for 3 hours at various temperatures between 550°C and 1100°C. Amorphous phases were obtained below 1000°C, and crystalline α–Al2O3 was formed at 1100°C. Although Al2O3 itself shows diamagnetism, the light doping of Fe ions into aluminium oxide induced a very weak ferromagnetism, but the ferromagnetism disappeared by longer annealing. Mössbauer spectra were composed of paramagnetic Fe2 +  and Fe3 +  species for samples heated below 750°C, and of paramagnetic Fe3 +  above 850°C, in addition to a magnetic sextet and relaxation peaks of Fe3 + . The magnetic and quadrupole interactions of the sextet and the relaxation peaks and the density functional calculations suggest that the lightly doped Fe3 +  ions are substituted at Al sites in the Al2O3 lattice.