Structural and Magnetic Properties of Fe-Doped Anatase TiO₂ Films Annealed in Vacuum

Structural and magnetic properties of Fe-doped anatase TiO₂ films fabricated by sol-gel spin coating are investigated. X-ray diffraction measurements reveal that Fe³⁺ ions are incorporated into the TiO₂ lattice. No ferromagnetism-related secondary phases and magnetic nanoparticles are observed in the films. The presence of electron paramagnetic resonance signals at g ~ 2.0 supports oxygen vacancies and/or defects generated in the films after annealing in vacuum. Magnetic measurements indicate that Fe-doped anatase TiO₂ films are ferromagnetic at room temperature. These observations suggest that oxygen vacancies and/or defects are energetically favorable for the long range Fe³⁺-Fe³⁺ ferromagnetic coupling in Fe-doped anatase TiO₂ films.