Effect of Bi2O3, MnCO3 additives on the structure and magnetic properties of M-type Sr-hexaferrites.

The effects of additives Bi 2 O 3 and MnCO 3 on the structural and magnetic properties of M-type Sr-hexaferrites (SrFe 12 O 19 ) prepared by a conventional solid-state reaction method were studied. The saturation magnetization value of undoped SrFe 12 O 19 is 71.8 emu/g; it increases to 72.6 emu/g and 74.2 emu/g with Bi 2 O 3 doping of 0.5 wt%and 1.0 wt%, respectively. However, abnormal grain growth occurs and the coercivity (H C ) decreases significantly in the 1 wt% Bi 2 O 3 -doped sample. Co-doping of 0.5 wt% Bi 2 O 3  + 0.5 wt% MnCO 3 is effective, because a higher saturation magnetization (73.1 emu/g) than that of undoped SrFe 12 O 19 could be achieved with a relatively large coercivity of ∼3.3 kOe. Based on the lattice parameter calculation, Bi 3+ preferably substitutes into Fe 3+ sites rather than Sr 2+ sites in M-type Sr-hexaferrite. The enhanced saturation magnetization can be attributed to the selective substitution of nonmagnetic Bi 3+ into the down-spin Fe 3+ site (4 f 1 or 4 f 2 ). [ABSTRACT FROM AUTHOR]