Influence of chromium substitution on structural and magnetic properties of BaFe 12O 19 powder prepared by sol–gel auto combustion method

Abstract

The nanocrystalline Cr 3+ substituted barium hexaferrite having generic formula BaFe 12− x Cr x O 19 (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 Ba 2+, Fe 3+ and Cr 3+ 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 BaFe 12− x Cr x O 19 was sintered at 900 °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 α-Fe 2O 3 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.