Magnetism of CoFe2O4 thin films annealed under the magnetic field

• CFO films were annealed in magnetic field with parallel and vertical directions.
• The film densification and grain size were changed by the applied magnetic field.
• A higher saturation magnetization is obtained under magnetic annealing.
• The enhanced magnetic anisotropy is observed after magnetic annealing.

Polycrystalline CoFe2O4 thin films were deposited on Si (100) substrates by chemical solution deposition with and without magnetic annealing. Magnetic field directions were applied parallel and perpendicular to the film surface during the magnetic annealing process. The variations of strain, microstructure and magnetic anisotropy of the films caused by the magnetic annealing are investigated. The results show that the film densification is promoted and grain morphology is changed by the magnetic annealing, which can be attributed to the promoting effect of magnetization force on the grain growing and grain boundary diffusing. Magnetic measurements indicate the enhancement of anisotropy and saturation magnetizations of the polycrystalline CoFe2O4 after magnetic annealing. Furthermore, the rotation of easy axis along the field direction, the increased occupation of Co2+ ions at B sites and the additional strain induced by the magnetic field are considered as the main reasons of the increased magnetic anisotropy.