Research On Preparation Process And Properties Of M Type Barium Ferrite Thin Films Prepared By Magnetron Sputtering Technology

M-type barium ferrite(Ba M) has high magnetocrystalline anisotropy, self-bias characteristics and excellent chemical stability, which has important applications in the millimeter-wave devices and magnetic recording mediums. Especially when the next generation of millimeter-wave magnetic devices such as circulators, isolators, filters are in service, Ba M ferrite material will be an important backbone material. However, after working at the millimeter wave band, the volume, weight and size of the magnetic devices will propose more stringent requirements for Ba M ferrite. Therefore, the traditional three-dimensional materials will gradually develop to thick and thin films. In order to meet the needs of the next generation of microwave devices, the Ba M films with a high degree of texture, C-axis oriented vertically, high remanence as well as have a certain thickness will be urgently needed.Ba M film with a certain thickness and a high degree of texture has been deposited on the sapphire substrates by radio frequency(RF) magnetron sputtering technique. The structure and magnetic properties of films were characterized by X-ray diffractometer(XRD), field emission scanning electron microscope(FESEM) and vibrating sample magnetometer(VSM), respectively, and the preparation process to prepare better texture Ba M film have been investigated. The optimal thickness of Ba M films were determined by studying the influence of film thickness on Ba M film crystal structure and magnetic properties. One adopts layered sputtering to prepare multilayer Ba M film, and analyzes its crystal structure, magnetic properties and stress. Finally, we obtain the bilayer films with better texture.The result shows that, the Ba M films deposited with a substrate temperature of 500℃, a gas pressure of 1.4 Pa and a post-annealing temperature of 850℃having a preferred C-axis perpendicular orientation. The Ba M films with the thickness of 40 nm ~ 90 nm have the largest coercivity and remanence ratio in the direction of perpendicular to the film plane, and show good magnetic anisotropy. One uses layered sputtering technology to deposited bilayer films. The initial 100 nm thick Ba M film has been annealed, which is regarded as a seed layer. Based on the 100 nm seed layer of Ba M film, one continues to deposit a 100 nm thick Ba M film annealed at proper temperature. The thickness of bilayer films is about 200 nm. In comparison with the 200 nm thick monolayer Ba M film, the bilayer films present better texture and preferred C-axis perpendicular orientation.