Magnetic Properties and Microstructures of YIG Thick Films Prepared by Screen-Printing

초록

YIG(Y3Fe5O12), a ferrimagnetic material also known as microwave ferrite, has been used in passive devices as thick film for MMIC(Monolithic Microwave Integrated Circuit). This study was focused the effect of the preparation process of thick film by screen-printing on microstructure and magnetic Proprties of Y3-xCaxFe4-xZrxO12 (x=0-0.4). In order to get a good densification of screen printed thick film, the CIP(Cold Isostatic Pressure) processing as a mechanical pressure was applied in printing of paste on alumina substrate. The saturation magnetization of thick film increased constantly with the higher Printing times as shown in figure 1, but the lower FMR line width was observed. The saturation magnetization (4πMs) appeared as maximum value of 1356 G for sample with the lower density sintered at 1300℃ and the ferromagnetic resonance(FMR) line width(△H) at x=0.2 showed the lowest value of △H = 185 for samples sintered at 1400℃ as substitution of Zr4+. The substitution behavior of octahedral Fe3+ ion by diamagnetic Zr4+ ion demonstrates that the saturation magnetization of the YIG thick film can be improved effectively due to the increasing of the total magnetic moment. Furthermore, reduction of anisotropy can also be accomplished by substitution of Fe3+ ions by Zr4+ of large ionic radius. In some different compositions of Y3-xCaxFe4-xZrxO12 (x=0-0.4), low line width values can be presented for magnetization range of 488 to 185 G. When the simultaneous addition Of two different ions such as Ca2+ and Zr4+ in this Study, together with a charge compensating divalent or tetravalent cation is applied, can be obtained with reduced line width for polycrystalline YIG sample. The lower FMR △H value can be obtained with the higher sintering density and saturation magnetization. Porosity, rather than anisotropy, acts as the dominant role to the resonance line width of low-density polycrystalline YIG. In order to investigate the combined affects of thickness of the