| Recently, with electronic devices and information systems quickly developing to miniaturization and multi-function, various of military , commercial microwave electronic device(se.g., circulators, isolators, phase shifters, etc.)toward the direction of high power, high performance, low power loss, low cost. In order to meet these new requirements, it is essential to prepare a high-quality, self-bias microwave ferrite thin film for reducing the exist size of microwave devices, and promote microwave electronic devices to integrated and planar.M-type hexa-barium ferrite(BaM)is one of the most productive microwave materials for their stable physical and chemical properties, good corrosion resistance, strong uniaxial magnetic anisotropy, and C-axis is the easy magnetization axis, large perpendicular magnetic anisotropy constant, high resistivity and dielectric constant at high-frequency, etc. However, no matter which microwave magnetic devices applications as research objectives, it is a crucial task to deposit films with a lot of requirements, such as saturation magnetization(Ms), squareness(SQ=Mr/Ms), C-axis orientation, surface roughness and film thickness, so it is hard to obtain such BaM films in practical processing community.To prepare these BaM thin films to meet our requirements, the effect of growth parameters (e.g., the buffer layer thickness, crystallization temperature, film thickness, annealing temperature and atmosphere, etc.) on the orientation, crystal quality and magnetic properties of BaM thin films are studied in this dissertation, optimum growth conditions for preparing BaM films by pulsed laser deposition(PLD)method are obtained. It also concludes that the BaM thick films'squareness decrease almost linearly prepared by the contiuous growth mode in our previous work. To decrease the decline rate of films'squareness, layer by layer alternate growth mode is proposed in this paper to prepare BaM thick films. Then, excellent performance double-layer and three-layer BaM composite thin films are successfully prepared by this alternate growth mode, SEM profile analysis studies show that these films'thickness reaches 1μm. Compare with the same thickness BaM thin films prepared by continuous growth mode, the layer by layer alternate growth mode significant reduce the decline of BaM thin films'squareness, the magnetic properties of BaM thin films received improving.In order to further enhance the squareness of BaM composite thin films, one layer of strontium-ferrite (SrM) been introduced into BaM double-layer composite thin films, and SrM/BaM composite thin films are prepared on MgO buffer layer. X-Ray Diffraction(XRD) studies show that excellent C-axis oriented thin films on sapphire substrates are obtained, the full width at half maximum (FWHM)of (0008) rocking curve is 0.7°for SrM/BaM double-layer composite thin films, indicating that these films are of a good quality. Scan electron micro-scope(SEM in short)measurement shows that these films's thickness reaches 1μm. Vibrate sample magnetometer (VSM) investigation shows that the perpendicular saturation magnetism and squareness for these SrM/BaM double-layer composite thin films are 182 emu/cm~3 and 0.85,respectively. Compare with BaM double-layer composite thin films, the squareness of SrM/BaM double-layer composite thin films increases by 10%. Compare with SrM single-layer thin films, the saturation magnetization of SrM/BaM composite thin films increase 12 emu/cm~3. Compare with BaM single-layer thin films, the squareness of SrM/BaM composite thin films increase by 3%. Therefore, the obtained SrM/BaM composite thin films absorb the merits of BaM thin films and SrM thin films. The properties of SrM/BaM double-layer composite thin films in our work are helpful to study the fabrication of SrM/BaM composite thick films and related devices. |
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