Formation of rod‐shaped BaFe12O19 nanoparticles with well magnetic properties

A facile approach to preparing rod‐shaped nanoparticles of barium ferrite was developed by combination of hydrothermal and annealing process in air. The magnetic nanorods with diameters ∼ 40 nm and lengths ∼ 150 nm were clearly visible in TEM and SEM images. Magnetic measurements showed that the rod‐like BaFe12O19 nanoparticles exhibited a great coercive field and high saturation magnetization of up to 4511 Oe and 67.3 emu/g, respectively. It is found that heat treatment in air can create less oxygen vacancies, which dramatically affects the Fe–O–Fe superexchange coupling. The results of this paper suggest that oxygen vacancies should be responsible for the decrease of saturation magnetization in nanosized magnetic materials.