Abstract
Co0.04Ti0.96O2 powders are fabricated by sol-gel method.The structure and magnetic properties are investigated under differentannealing conditions systematically with emphasis on the influence ofoxygen pressure. Pure anatase structure was acquired for all the samplesannealed at 450 degrees C for one hour. The samples annealed in airexhibit evident room-temperature ferromagnetism (RTFM) with a smallmagnetic moment of 0.029 μB per Co atom and coercivity Hcof 26 Oe, while the samples annealed in vacuum have strong RTFM with alarger magnetic moment of 1.18 μB per Co atom and Hc of430 Oe. The zero-field spin echo nuclear magnetic resonance spectrum of59Co is obtained to prove the existence of Co clusters inthe latter samples, implying that the Co clusters are responsible forthe strong RTFM in the samples annealed in vacuum. No Co cluster couldbe observed using both XPS and NMR techniques in the samples annealedin air, implying that the RTFM found in these samples is intrinsic.
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