Preparation And Properties Of Cobalt Ferrite Thin Films

Recently, the fabrication, structures, properties and applications of perpendicular megnetic recording thin films have gained significance in the novel materials science all over the world. Perpendicular magnetic recording thin films have been paid much attention for their high recording density, high recording speed, good thermal stability, mechanical wear-resisting, and their applications in perpendicular magnetic recording, heat-assisted perpendicular magnetic recording, magnetic-optical recording et al. CoFe2O4 thin films are being investigated extensively in the perpendicular magnetic recording materials. Because CoFe2O4 thin films have large covercivity, saturation magnetization and magnetocrystalline anisotropy, they are the appropriate materials for perpendicular magnetic recording hard disk. In this paper, the fabrication process, micro-structure and properties of CoFe2O4 thin films were systematically studied from experimental aspect. In additionally, this paper studied about the target materials dispensing and fabrication process of Co_0.7Fe_2.3-xMn_xO₄ used in heat-assisted magnetic recording, then researched about fabrication process and magnetic properties of Co_0.7Fe_1.7Mn_0.6O₄ thin film.In the study of CoFe2O4 thin films, RF magnetron sputtering technology have been utilized to fabricate the CoFe2O4 thin films on 7mm×7mm Si(100) substrates. After the fabrication, the thin films were sintered by CTA and RTA. By the experiment, the optimum process were gained and it was substrate temperater of 350℃, sputter pressure of 1.0Pa, sputter power of 120W, film thickness of 100nm, annealing temperature of 700℃, heat-up speed rate of 2.5℃/min and thermal retardation time of 3h. Analyses by the aid of atom force microscopy (AFM) and X-ray diffraction (XRD) and measurement reveal that the thin films have good magnetic properties and perpendicular anisotropic properties in the optimum process. And the thin films have the parallel covercivity of 3.18kOe, perpendicular covercivity of 11.76kOe and saturation magnetization of 210.61emu/cm³, respectively. Meanwhile, the effects of parameters of the films fabrication process on the microstructures and properties of the thin films have been investigated. In the study of Co_0.7Fe_2.3-xMn_xO₄ target and thin films, the optimum target materials dispensing is Co_0.7Fe_1.7Mn_0.6O₄ when x=0.6. The Curie temperature of this point is 335.8℃. And it is much better to siter the target at 1250℃after pre-sintering than direct sintering. Then the better process of the thin film fabrication were also gained and it was substrate temperater of 450℃, O₂/(Ar+ O₂)=10%, sputter pressure of 1.0Pa, sputter power of 100W, annealing temperature of 900℃, heat-up speed rate of 2.5℃/min and thermal retardation time of 3h. The thin films have the perpendicular covercivity of 1.24kOe and parallel covercivity of 0.79kOe at this processing parameter. This experiment approved that it is possible to fabricate heat-assisted perpendicular magnetic thin films by the target materials dispensing.