Coercivity Mechanism of SrO ·6 Fe2O3 Ferrite Magnets

The relation between the alignment dependence of the coercivity (ALDC) and the angular dependence of the coercivity (ANDC) for SrO·6Fe2O3magnets with various alignments is investigated. The coercivity of the SrO·6Fe2O3magnet is found to decrease as the alignment improves, which is similar to the behavior of Nd-Fe-B sintered magnets. It is expected that the crust of the grains simultaneously reverses via a magnetic domain wall that jumps through a number of grains. The ANDC of SrO·6Fe2O3decreases with increasing magnetic field angle until 40°, after which the coercivity gradually increases until 70°. The angle of the magnetization reversal area (01) of the SrO·6Fe2O3magnets, obtained from the ALDC, is 41° which is larger than that of Nd-Fe-B or Nd-Dy-Fe-B sintered magnets. The calculated ANDC using 01 = 41° and a Gaussian distribution of o = 70 for the alignment distribution function shows that the ANDC decreases from φ = 0° and agrees well with the experimental results until φ = 40°, where φ is the angle between the magnetization direction of the magnet and the magnetic field. These results strongly support the coercivity mechanism obtained from Nd-Fe-B sintered magnets whereby, in the SrO·6Fe2O3magnets, the magnetic domain wall is pinned at the tilted grains and when the magnetic domain wall becomes de-pinned, the magnetic domain wall jumps through a number of grains.