Structure-Magnetism Correlation in 5% Fe-doped TiO2 Nanostructures Via Mechanical Alloying

Abstract

Nanocrystalline TiO2 powders doped with 5 wt% Fe were synthesized by mechanical alloying (MA) with milling times ranging from 0 to 48 h, and their magnetic behavior was systematically investigated. Structural evolution was characterized by X-ray diffraction (XRD) and Rietveld refinement, while magnetic properties were assessed at room temperature using vibrating sample magnetometry (VSM). The structural analysis revealed a progressive anatase-to-rutile transformation with increasing milling time. Metallic Fe reflections, detected at the early stages, diminished as milling progressed, indicating Fe incorporation into the TiO2 lattice. This structural evolution was accompanied by decreasing crystallite size and increasing microstrain, consistent with enhanced defect generation. Magnetic characterization demonstrated weak ferromagnetism in all samples, with saturation magnetization (Ms) increasing steadily with milling time. The enhancement of Ms is attributed to defect-mediated exchange mechanisms involving Fe substitution at Ti sites and the formation of oxygen vacancies, which act as centers for magnetic interactions. These results underline the strong correlation between structural defects and emergent ferromagnetism in Fe-doped TiO2 nanostructures, emphasizing the potential of mechanical alloying as an efficient route for engineering dilute magnetic oxides with tunable properties.