Coercivity Mechanism of SrO $\cdot6$ Fe2O3 Ferrite Magnets

The relation between the alignment dependence of the coercivity (ALDC) and the angular dependence of the coercivity (ANDC) for SrO·6Fe
₂
O
₃
magnets with various alignments is investigated. The coercivity of the SrO·6Fe
₂
O
₃
magnet 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·6Fe
₂
O
₃
decreases 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·6Fe
₂
O
₃
magnets, 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·6Fe
₂
O
₃
magnets, 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.