Polycrystalline Bi substituted YIG ferrite processed via low temperature sintering

Abstract

Polycrystalline Bi substituted YIG ferrite (i.e., Y3-xBixFe5O12) has been widely studied due to its high electrical resistivity, moderate to high magnetization and permeability, and relatively low processing cost. Furthermore, it is suitable for large-scale industrial production making it a viable material for mass-produced filters, inductors, isolators, and other rf components. However, low temperature co-fired ceramic technology requires sintering temperatures below ∼960 °C (i.e., the approximate melting point of the silver electrodes are ∼961 °C) while maintaining a low ferromagnetic resonance linewidth (ΔH) and other desirable properties. This work reports the effect of bismuth addition on the ferromagnetic properties of low-temperature sintered Y3-xBixFe5O12 (x = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2) garnet ferrites. The microstructure, magnetic properties, and gyromagnetic properties of the Bi-YIG samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and ferromagnetic resonance (FMR). Results support the processing of pure phase garnet, with moderate values of saturation magnetization and FMR linewidth for x = 0.9. Moreover, the Fano algorithm was shown to provide superior fitting to asymmetric FMR spectra allowing for very accurate measurement of ΔH.