Long-range ferromagnetic ordering at room temperature in Co⁺ implanted TiO₂ nanorods

Long-range ferromagnetic ordering at room temperature is reported for post-annealed TiO₂ nanorods doped with Co²⁺ by an ion implantation technique. The catalyst free anatase TiO₂ nanorods are grown normal to the substrate plane. A Curie temperature of ∼320 K was recorded for a ∼9 at.% Co doped sample. Electronic structural studies confirm the substitutional Co in the Ti lattice site. Microstructural studies show the presence of extended defects, where a minor nonuniformity in doping concentration helps to sustain the intrinsic ferromagnetic ordering in Co doped TiO₂ at room temperature. The projected nanorod tip size is found to be smaller than a single magnetic domain, which may lead to an increased signal-to-noise ratio for magnetic recording.