Influence of chromium substitution on structural and magnetic properties of BaFe12O19 powder prepared by sol-gel auto combustion method

The nanocrystalline Cr3+ substituted barium hexaferrite having generic formula BaFe12-xCrxO19 (where x = 0.00, 0.25, 0.50, 0.75, and 1.00) samples were synthesized by sol-gel auto-combustion technique. The precursors were prepared by using stoichiometric amounts of Ba2+. Fe3+ and Cr3+ nitrate solutions with citric acid as a chelating agent. The metal nitrate to citric acid ratio was taken as 1:2 while pH of the solution was kept at 8. The thermal decomposition of nitrate-citrate gels of as-prepared powder was investigated by TG/DTA. The as-prepared powder of BaFe12-xCrxO19 was sintered at 900 degrees C for 8 h. The sintered powder was characterized by XRD, EDAX, SEM and VSM technique. The pure barium hexaferrite shows only single phase hexagonal structure, while for the samples at x = 0.25, 0.50, 0.75 and 1.00 shows alpha-Fe2O3 peaks with M-phase of barium hexaferrite. The lattice parameters (a and c) decreases with increase in chromium content x. The particle size obtained from XRD data is in the range of 30-40 nm which confirms the nanocrystalline nature of the samples. The magnetic properties were investigated by means of vibrating sample magnetometer (VSM) technique. The saturation magnetization (M-s), remanence magnetization (M-r), coercivity (H-c) and magneton number (n(B)) decreases with increase in chromium content x. (C) 2011 Elsevier B.V. All rights reserved.