Enhanced electrical and ferrimagnetic properties of bismuth substituted yttrium iron garnets

Y3-xBixFe5O12 (0 ≤ x ≤ 1.0) powders are successfully prepared by sol-gel auto-combustion method. The structural, morphological, electrical and magnetic properties of bismuth substituted YIG are systematically studied and reported. The phase formation and position of vibrational modes are studied using XRD, FTIR and Raman Spectroscopy respectively. The XRD patterns of Bi-YIG powders confirm the formation of polycrystalline, single phasic and cubic garnet structure with average crystallite size around 39 nm. FTIR spectra show well resolved bands corresponding to the tetrahedral and octahedral voids of Fe–O in YIG which is characteristic of garnets. The observed translational Raman active vibrational modes confirm the presence of cubic YIG phase. SEM micrographs reveal the formation of adense homogenous network of spherical shaped Y3-xBixFe5O12 grains. Magnetic properties of Bi-YIG show an enhancement compared to the host YIG, confirming the presence of ferrimagnetic ordering at room temperature. The observation of hysteresis loop along with low coercivities are typical of soft magnetic materials. Impedance measurements of Bi-YIG show an increase in electrical resistance up to two orders compared to YIG. The Bi-YIG sample having x = 0.6 exhibits a low dielectric loss equal to 0.045 and a low conductivity of the order of 10−6 Scm−1 at 100 kHz. The observations from magnetic and electrical studies illustrate the distinct role played by bismuth ions in the YIG lattice making it a potential candidate for microwave and magnetic-optical applications. © 2021 Elsevier B.V.