Preparation And Research Of Low-dimensional Bi-YIG Magneto-optical Materials

With the development of optical communication and information processing technology, magneto-optical materials would be widely applied in fields of optical communication, magneto-optical (MO) storage, strong absorbing of infrared and electromagnetic wave, ets. Up to now, the most thoroughly researched and broadly applied magneto-optical material is the rare earth iron garnet (Re₃Fe₅O₁₂, Re is the element of rare earth), in which Bismuth substituted iron yttrium iron garnet (Bi-YIG) has been actively pursued because of its excellent magneto-optical performance. Low-dimensional MO materials, including nanoparticle, thin solid film and nanofibers, have received much attention and suggested a wide range of applications. Magnetic nanoparticles are widely applied in density MO storage and strong absorbing of electromagnetic wave. MO thin films are highly valued in the field of optical integration technology. MO fibers, with high density of interspaces among them, permit multiple reflections and absorptions of electromagnetic waves on their surfaces, indicating of a good candidate for the absorbing material of electromagnetic wave.Based on the excellent magneto-optical performance of Bi-YIG and the applications of Low-dimensional MO materials mentioned above, in this paper, nanoparticles of Bi-YIG were prepared following co-precipitation method and the influence of PH value on the size of the Bi-YIG particles was discussed; Bi-YIG thin films were deposited on quartz glass by magnetron sputtering followed by the deposition of DLC (diamond like carbon) film on the obtained MO film surface, so that a reflection reducing effect of the MO film is obtained; YIG (yttrium iron garnet) superfine fibers were also prepared by electrospinning, and the influence of addition rate of electrospinning solution as well as environmental humidity on the process of electrospinning was investigated. Subsequently, details are discussed.1. Nanoparticles of Bi substituted yttrium iron garnet were prepared following co-precipitation method, and the hydroxide precursor was annealed at different temperature. Bi-YIG Nanoparticles were characterized by X-ray diffraction (XRD). The result shows that the samples get better crystallization at higher temperature, and single garnet phase was obtained when the treatment temperature was 650℃. The hydroxide precursor and Bi-YIG particles were observed by Transmission electron microscope (TEM), and it is found thatPH value was important influencing factor for the size and distribution of the particles. The sizes of particles were minimized when the PH value was 12, with the size around 10nm. Besides, the Bi-YIG particles were prepared with metal oxide, and characterized by XRD. The preparation temperature of Bi-YIG prepared by co-precipitation method was lowered at least by 500℃ comparing with that prepared with metal oxide.2. Bi-YIG thin films were deposited on quartz glass by magnetron sputtering and annealed at the temperature of 600℃-700℃. The surface morphologies of the obtained Bi-YIG films were observed by Atomic force microscopy (AFM). The results show that the surface morphologies of the films were some kind of concave with ridges around, and the size of the concave was about 10 μm. Moreover, there were cracks on the top of the ridge-regions with width of 340 nm. The films were characterized with XRD. The results show the films are a single garnet phase and crystallized better with the increase of treatment temperature. The size of crystal grain of MO film, being scores of nanometers, was calculated based on the results of XRD. And it is in good accordance with AFM observation. Then, DLC (diamond like carbon) thin films were deposited on the surface of MO film and characterized by Raman spectra. The spectra indicates that the films are typical DLC. After that, the composite films and Bi-YIG films were characterized by infrared visible transmission spectrum. It is revealed that the transparence of MO films is increased by depositing DLC.3. Metallic organic compounds which contain iron and yttrium were dissolved in organic solvent, so a kind of solution was obtained ,with which, the superfine fibers were prepared by electrospinning. After annealing, the YIG (yttrium iron garnet) superfine fibers were prepared. The fibers before and after annealing were observed by Scanning electron microscope (SEM), and the fibers after annealed were characterized by XRD. The results indicated that addition rate of the solution and environmental humidity were two major influencing factors for the process of electrospinning, and better fibers were obtained with smaller addition rate and relatively low humidity. The diameters of the composite fibers were between 500-1000nm. After annealing, the diameters were between 100-200nm, and the Y₃Fe₅O₁₂ phase was obtained along with YFeO₃.