Preparation and magneto-optical properties of BiY2Fe5O12 organic nanocomposite

Abstract

Bi-substituted yttrium iron garnet with a composition of BiY2Fe5O12 (Bi-YIG) nanoparticles was prepared via mechanochemical processing and subsequent heat treatment. The maximum milling time was 8 h and the annealing was carried out at different temperatures up to 1000 degrees C for 4 h. Phase formation of the as-milled and annealed powders was investigated by X-ray diffraction (XRD). This investigation shows that there was no trace of garnet phase in the as-milled powder or the powders annealed below 800 degrees C. In the XRD patterns of the powders annealed above 800 degrees C, the peaks belonging to the garnet phase appeared and a single-phase garnet was finally obtained at 950 degrees C. Magnetic parameters of the powders were measured, using a SQUID unit, and a saturation magnetization of 22Am(2)/kg was obtained. Mean crystallite size of the single-phase powder, which was evaluated by Scherrer's formula was about 45 nm. Morphology of the powders was investigated by TEM, which shows that the particles were agglomerated. The single-phase powders were then dispersed in an organic binder for various Bi-YIG/binder weight ratios and for various dispersing times up to 80 h to obtain magnetic inks. Particulate films were made by the spin-coating method, using the magnetic inks. Magneto-optical properties (Faraday rotation) of the spin-coated films were investigated in the visible wavelength range of 470-625 nm. The results show that as Bi-YIG/binder weight ratios increases, the values of the Faraday rotation spectra increase too and their maximum values shift to shorter wavelengths. (c) 2007 Elsevier B. V. All rights reserved.