TiO2 nanocrystals doped with 1%, 5% and 10% Co/TiO2 and 10% M (M=Fe, Mn and Ni) were prepared by the sol–gel technique and characterized using X-ray diffraction and SQUID. The as-prepared samples are found to be paramagnetic at room temperature, with the magnetic susceptibility following the Curie–Weiss law in the investigated range of 2–370 K. However, transformation from paramagnetism to room-temperature ferromagnetism (RTFM) for the 5% Co/TiO2 was observed by hydrogenating the sample at 573 K while the 1% sample remained paramagnetic. As the percentage of Co was increased from 5% to 10% the Curie temperature increased from 390 K to 470 K determined via extrapolation. Transformation from paramagnetism to room-temperature ferromagnetism (RTFM) was also observed by hydrogenation of 10% Fe/TiO2 at 573 K for 6 h. X-ray diffraction of the hydrogenated sample shows only single phase TiO2 structure suggesting that the observed RTFM may be intrinsic but
magnetic studies may suggest the possibility of Fe nanoparticles.
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