Effect of Co stearate addition on magnetic properties of anisotropic SrFe2W-type ferrite magnets

We investigated the effect of Co stearate as a new reducing agent, with SiO2 and CaO additives, on the magnetic and physical properties of SrFe2 W-type hexagonal ferrite. We found that the magnetic properties of SrO-8.5Fe(2)O(3) were considerably improved by adding 0.3 wt% of Co stearate, 0.3 wt% of SiO2, and 0.7 wt% or CaO simultaneously. The optimum condition for preparing magnets were as follows: chemical analysis composition, Sr0.9732+Si0.0884+Ca0.1662+ Co0.0082+Fe1.3812+Fe16.0643+O27; semisintering condition, 1350 degreesC x 4.0 h in nitrogen gas atmosphere; drying condition, 200 degreesC x 0.5 h in air; sintering condition, 1160 degreesC x 1.5 h in nitrogen gas atmosphere. The resulting magnetic and physical properties were J(m) = 0.48 T, J(r) = 0.44 T, H-cJ = 189.0 kA/m, H-cB = 178.8 kA/m, (BH)(max) = 34.7 kJ/m(3), T-c = 493 degreesC, and n(B) = 28.8 mu(B). The temperature dependences of J(m), H-cJ, and K-A were measured in these samples; KA and HA were 3.10 x 10(5) J/m(3) and 1303 kA/m at 20 degreesC, respectively. The temperature dependence of K-A and H-A was similar to that in M-type hexagonal ferrite.