Synthesis and Magnetic Properties of Carbon Doped and Reduced SrTiO3 Nanoparticles

We report on the studies of the synthesis, structural, and magnetic properties of undoped SrTiO3 (STO), carbon-doped STO:C, and reduced STO STO:R nanoparticles. Fine (similar to 20-30 nm) and coarse (similar to 100 nm) nanoparticles with a single phase of cubic perovskite-type structure were sintered by thermal decomposition of SrTiO(C2O4)(2). Magnetization loops of fine STO:C and STO:R nanoparticles at low temperatures and an almost linear decrease in magnetization with temperature indicate the realization of a soft, ferromagnetic state in them, with a pronounced disorder effect characteristic of doped dilute magnetic semiconductors. Oxidation and particle size increase suppress the magnetic manifestations, demonstrating the importance of surface-related defects and oxygen deficiency in the emergence of magnetism. It was found that oxygen vacancies and doping with carbon make similar contributions to the magnetization, while complementary electron paramagnetic resonance, together with magnetization measurement studies, show that the most probable state of oxygen vacancies, which determine the appearance of magnetic properties, are charged F+ oxygen vacancies and C-impurity centers, which tend to segregate on the surface of nanoparticles.