Ferromagnetism in Electrospun Co-doped SrTiO₃ Nanofibers

By employing electrospinning technique, subsequent calcination in air and annealing process in hydrogen, uniform Co-doped SrTiO₃ nanofibers with concentrations of Co between 0 and 0.20 were successfully produced. Their morphologies and detailed structures were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction. And, the chemical states of Co were determined by X-ray photoelectron spectroscopy. It was shown that, after calcination, Co²⁺ was well incorporated into the perovskite structure of SrTiO₃, and the nanofibers possessed smooth surface with diameters of 50–100 nm. Magnetic properties of the hydrogen-annealed and -unannealed nanofibers were both measured by physical property measurement system from 50 to 300 K. It was explored that the Co addition and the hydrogen annealing process were both very important to the generation of the observed ferromagnetism in SrTi_1−x Co _x O₃:H₂ nanofibers. In hydrogen-annealed SrTi_0.80Co_0.20O₃:H₂ nanofibers, a saturation magnetization of 0.74 emu/g and an average moment of 0.122 μ_B/Co were obtained. The origins of the enhanced ferromagnetism in SrTi_1−x Co _x O₃:H₂ nanofibers were analyzed according to the chemical state of Co and the mediation of oxygen vacancies.