High-Temperature DC-Magnetisation Investigation on Undoped and 5 at.% Cobalt Incorporated TiO2 Nanopowders
Tóm tắt
Nanocrystalline samples of both undoped TiO2 and with 5 at.% Co at cationic sites were prepared by a simple chemical route. X-ray diffraction study of these samples revealed an increase in lattice parameters due to incorporation of Co in the TiO2 lattice and possibly due to formation of oxygen vacancies. No traces of crystalline Co or any other secondary phases could be detected. High-temperature SQUID measurement of these samples exhibited ferromagnetic signature up to 700 K, implying that the Curie temperature of doped and undoped TiO2 exceeds 700 K. Vacuum annealing of both types of samples enhanced the ferromagnetic character. The as-prepared and vacuum-annealed Co incorporated TiO2 samples, in addition to the ferromagnetic character, also exhibited a paramagnetic signal. All these measurements strongly support the role of defects in inducing room-temperature ferromagnetism in undoped and Co doped TiO2 nanopowders, which can be explained using the bound magnetic polaron model.
Từ khóa
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