Correlation between oxygen vacancies and room-temperature ferromagnetism in Ti0.94Co0.03La0.03O2 nanoparticles influenced by different post annealing treatment
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The correlation between oxygen vacancies and room-temperature ferromagnetism in Ti0.94Co0.03La0.03O2 nanoparticles is investigated by treating the samples in different post annealing process. Ti0.94Co0.03La0.03O2 nanoparticles were prepared via sol–gel method followed by post annealing under vacuum or in air. The samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectroscopy, Raman spectra, and magnetic measurement techniques, respectively. The characterizations confirmed the incorporation of substituting Co and La atoms into anatase TiO2 lattice. More oxygen vacancies were introduced into Ti0.94Co0.03La0.03O2 when annealed under vacuum. The vacuum annealed sample exhibits typical ferromagnetic behavior with well-defined hysteresis loops and a saturation magnetization, while the air annealed sample displays feebler ferromagnetism, which is transformed to paramagnetism afterwards when further annealed in air. All measurements strongly support the decisive role of oxygen vacancies in inducing room-temperature ferromagnetism in Ti0.94Co0.03La0.03O2, which can be explained using the bound magnetic polaron model.
KeywordsDiluted magnetic semiconductors TiO2 Ferromagnetism Oxygen vacancy Annealing treatment
This work was supported by the Open Fund of Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials (No. QMNEM1610).
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Conflict of interest
The authors declare that they have no conflict of interest.