Ferromagnetism in barium titanate nanoparticles. Effect of annealing in hydrogen atmosphere on magnetic properties

Dependences of magnetization on magnetic field strength were studied for both the nanostructured and the bulk ferroelectric barium titanate. It has been found that nanostructured barium titanate demonstrates ferroelectric, ferromagnetic and diamagnetic properties simultaneously. The annealing of nanostructured barium titanate in hydrogen atmosphere under experimental conditions leads to a significant increase of the spontaneous magnetization and decrease of the diamagnetic response. Analysis of experimental results shows that defects in grains surfaces of the barium titanate nanoparticles (probably oxygen vacancies) are mainly responsible for electron states, which produce ferromagnetic and diamagnetic responses.