The magnetic property of carbon-doped TiO₂

Despite carbon and TiO₂ are nonmagnetic, we detected ferromagnetism at room temperature over samples of carbon-doped TiO₂. The materials were prepared by standard solid-state reaction and sintered either in an argon or nitrogen atmosphere. According to Raman results, the samples sintered in nitrogen showed lower D-bond (disordered) and G-bond (graphitic) concentration, plausibly a result of nitrogen incorporation into the carbon-doped TiO₂ materials. All the samples are ferromagnetic at room temperature. With increase of carbon concentration, there is decline of magnetic moment per carbon (in carbide form) due to antiferromagnetic interaction among the carbon atoms. Compared to the sample sintered in argon, the one sintered in nitrogen is lower in magnetic moment due to partial replacement of carbon atoms by nitrogen atoms. We found that the electrons-mediated mechanism is more suitable than the holes-mediated one for the explanation of ferromagnetism of the carbon-doped TiO₂ materials.