The effect of nano sized SrFe12O19 additions on the magnetic properties of chromium-doped strontium-hexaferrite ceramics

Strontium hexaferrite (SrFe12O19) which crystallizes in the hexagonal system and has a uniaxial magnetoplumbite structure, displays distinctive magnetic characteristics, good chemical stability, good tribological properties and a weak temperature dependent coercivity at about room temperature. In the present work the synthesis conditions for the solid-state preparation of the chromium-doped hexaferrite SrCr0.3Fe11.7O19 were optimised and the effect on the magnetic properties of this compound of additions of nanosized SrFe12O19 was studied. The nanosized SrFe12O19 additive, synthesized by the citrate-nitrate reaction, was substituted in varying amounts for a commercial calcium silicate borate sintering additive mixture. A combination of 0.75 wt% of nano-sized SrFe12O19 with 0.75 wt% of the commercial additive increases the intrinsic coercivity, remanence magnetization and rectangularity ratio and results in superior magnetic properties than obtained with 1.5 wt% of nanosized SrFe12O19 or the commercial sintering additive alone.