Presence of Room Temperature Ferromagnetism in CO2+ Doped TiO2 Nanoparticles Synthesized through Shape Transformation

Abstract

New approach for synthesis of Co2+ doped TiO2 nanoparticles showing room temperature ferromagnetic behavior, through shape transformation of hydrothermally treated scrolled titania nanotubes in the presence of Co2+ ions is described. The XRD and ICP measurements demonstrated successful incorporation of 0.46 at % Co2+ ions in preserved anatase crystal structure of TiO2 nanoparticles, without presence of Co-oxide Clustering, metallic Co, or Various Co-Ti oxide species. HRTEM measurements revealed that majority of the nanoparticles have polygonal shapes with average dimension of similar to 6-10 nm. Obtained Value of 3.06 eV for band gap energy of Co2+ doped TiO2 nanoparticles explained altered optical properties of TiO2 matrix and indicates narrowing of the electronic properties in respect to the undoped anatase TiO2 nanomaterials. The Co2+ doped TiO2 nanocrystals enabled synthesis of optically transparent film that shows room temperature ferromagnetic ordering with a saturation magnetic moment of 0 25 mu B per Co atom The proposed explanation for room temperature ferromagnetic behavior is based oil the presence of critical amount of oxygen vacancies that mediate interaction between Co2+ spins trapped in the lattice Structure of titania nanoparticles with undercoordinated surface defect sites.