MAGNETIC-PROPERTIES OF ANISOTROPIC SR-LA-SYSTEM FERRITE MAGNETS

An experiment was carried out to investigate the effect of La2O3 addition to the magnetic and physical properties of strontium ferrite magnets. It was found that the La2O3, addition to SrO. 6Fe2O3, (stoichiometric composition) was very useful in stabilizing the magnetoplumbite structure and that these Sr-La-system ferrites had excellent properties as a permanenent magnet. Compositions were chosen according to the formula [formulla omitted] where n was varied between 5.0 and 6.5, and x between 0 and 5.0. The optimum conditions for making magnets and some properties of typical specimens were as follows: The chemical analysis composition was [formulla omitted] The semisintering condition was 1250°C for 1 h in oxygen, and the sintering condition 1300°C for 0.5 h in oxygen. Magnetic and physical properties were Jm = 0.435 T (4.35 kG), Jr = 0.425 T (4.25 kG), H,j = 244.0 kA/m (3.05 kOe), H,B = 236.0 kA/m (2.95 kOe), (BH)max = 36.0 kj/m3 (4.5 MGOe), σ,= 85.8 × 10-6 Wb. m/kg (68.3 emu/g) (at 25 °C), T, = 447 °C, KA = 3.45 × 10s J/m3 (3.45 × 106 erg/cm3), H = 1664 kA/m (20.8 kOe), nB = 20.0 μB, and D = 5.04 Mg/m5 (5.04 g/cm3). © 1990 IEEE