Room temperature ferromagnetism in Cu2+ doped TiO2 nanocrystals: The impact of their size, shape and dopant concentration

• Cu2+ doped TiO2 nanocrystals from titania nanotubes.
• Anatase crystalline structure of TiO2 matrix was detected in all samples.
• RT ferromagnetizm (H ∼ 200 Oe) in Cu2+ doped TiO2 nanocrystals.
• Magnetic properties are influenced by the Cu2+ conc., size and shape of nanoparticles.

Cu2+ doped TiO2 nanocrystals were synthesized using dispersions of titania nanotubes in the presence of Cu2+ ions as a precursors. The morphologies of nanotubular titania precursors and resulted Cu2+ doped TiO2 nanocrystals were characterized by TEM. Structural and optical properties were studied by XRPD analysis and UV–vis spectroscopy in reflectance mode, respectively. Their magnetic properties were investigated using SQUID magnetometer. Tetragonal anatase crystalline structure was confirmed in all synthesized samples. Polygonal (d ∼ 15 nm) and spheroid like (length, up to 90 nm) Cu2+ doped TiO2 nanocrystals in samples synthesized at different pHs were observed by TEM. Ferromagnetic ordering with almost closed loop (Hc ∼ 200 Oe) was detected in all Cu2+ doped TiO2 nanoparticle films. The saturation magnetization values varied depending on the Cu2+ concentration, nanoparticles shape, size and consequently different number of oxygen vacancies. This study revealed possibility to control magnetic ordering by changing the shape/aspect ratio of Cu2+ doped TiO2 nanocrystals.

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