MAGNETO-OPTICAL PROPERTIES OF Bi-YIG NANOPARTICLES DISPERSED IN THE ORGANIC BINDER

초록

Since bismuth yttrium iron garnet (Bi-YIG) films have a large Faraday rotation in visible wavelength, the Bi-YIG could be the most attractive materials for magneto-optical devices[1]. Ultrasonic irradiated in a liquid produces the cavitation process[2]. The cavitation leads to hot-spot and microjet impacts on the materials which can result in reaction activating, particle size reduction, surface cleaning, and so on. In this study, Bi-substituted YIG (Bi18Y12Fe5O12) nanoparticles were prepared by coprecipitation with ultrasonic irradiation method and examined the magneto-optical properties of the dispersed particles in the organic binder. As a result of calcination at 650℃, the particles were identified as garnet structure by X-ray diffraction, the particle size was below 20nm and the saturation magnetization was 17 emu/g. Their particles were dispersed in the organic binder, then were coated on glass substrate by a spin coater. As a dispersion time was increased from 1 to 5hr, the particles were more uniformly distributed in the thin films and the surface roughness of the films was below 2nm, the film thickness was about 550nm. With increasing the weight fraction of the particles in the organic binder from 5 to 20wt.%, the absorption coefficient of coated thin films increased from 0.25 to 1.0 degree at 450nm wavelength. Also, the coefficient reduced a little according to increase of the dispersion time. Faraday rotation of the thin films was observed in the region of the wavelength 410∼520nm and figure of merit (FOM) was shown at 0.5∼3.2. Thus, Bi-YIG nanopaticles prepared by coprecipitation with ultrasonic irradiation method have the possibility to be applied to magneto-optical devices working in the visible wavelength region. [1] N. Kawai et al. IEEE Tran. Magn. 30 (1994) 4446 [2] D. Peters. J. Mater. Chem. 6 (1996) 1605