Phase analysis and cation distribution correlated with magnetic properties of spinel Ba<inf>1−x</inf>Sr<inf> x</inf>Fe<inf>2</inf>O<inf>4</inf> ferrites prepared at different annealing temperatures

Abstract

Nano Ba1-xSrxFe2O4 samples were prepared by sol-gel autocombustion procedure. The phases developed due to different annealing temperatures and Sr-substitution amounts were determined by X'Pert HighScore Plus software. The effect of composition and annealing temperature on the lattice parameters and the crystallite size was investigated using X-ray diffraction technique. Rietveld analysis has been performed to determine the cation distribution between different crystallographic sites upon the Sr-substituted BaFe2O4 sample. Sr ion was found to prefer residing at 4a(II) site and the coordinates of this site dramatically changed with the Sr content (x). Fourier transform infrared spectrometry (FTIR) confirmed the orthorhombic structure of BaFe2O4 and the presence of the hexagonal structure ascribed to Ba0.5Sr0.5Fe2O4 for Sr-substituted samples. BaFe2O4 and Ba0.5Sr0.5Fe2O4 samples prepared at 700 °C revealed hysteresis loop with wasp-waist nature. The saturation magnetization and coercivity changed irregularly upon varying the annealing temperatures. For Ba1-xSrxFe2O4 samples annealed at 900 °C, the saturation magnetization changed depending on the amount of Sr doping in the sample. Ba0.5Sr0.5Fe2O4 has the lowest coercively (424 Oe) at 700 °C annealing temperature, while its highest saturation magnetization (3.83 emu/g) is obtained at 1050°C. Many factors were considered to explain the irregular behavior of coercivity in the Ba1-xSrxFe2O4 nano system.