Relation between the alignment dependence of coercive force decrease ratio and the angular dependence of coercive force of ferrite magnets

• Coercivity decrease ratio of ferrite magnets increases, as temperature increases.
• Angle of reverse magnetization area expands from the calculation results.
• Angular dependence of coercivity also changes as temperature increases.
• As temperature increases, angular dependence of coercivity becomes smaller.
• Angular dependence of coercivity is explained by angle of reverse magnetization area.

The relation of the coercive force decrease ratio (CFDR) and the angular dependence of the coercive force (ADCF) of ferrite magnets and their temperature properties were investigated.When we compared that against the angle of the magnetization reverse area obtained from these calculation results, which was obtained from the Gaussian distribution of the grain alignment and the postulation that every grain follows the Kondorskii law or the 1/cos θ law, and against the angle of the reverse magnetization area calculated from the experiment CFDR data of these magnets, it was found that this latter expanded at room temperature, to 36° from the calculated angle, for magnet with α=0.96. It was also found that, as temperature increased from room temperature to 413 K, the angle of the reverse magnetization area of ferrite magnets obtained from the experiment data expanded from 36° to 41°.When we apply these results to the temperature properties of ADCF, it seems that the calculated ADCF could qualitatively and reasonably explain these temperature properties, even though the difference between the calculated angular dependence and the experimental data still exists in the high angle range.These results strongly suggest that the coercive force of these magnets is determined by the magnetic domain wall motion. The magnetic domain walls are strongly pinned at tilted grains, and when the domain walls are de-pinned from their pinning sites, the coercive force is determined.