Evaluation of magnetic anisotropy in oriented plate-shaped strontium ferrite particles

Plate-shaped hexagonal SrFe12O19 particles, synthesized using potassium bromide as the molten salt flux, were dispersed in the resin using a planetary ball mill. Oriented sheets were prepared by coating the dispersion onto the films under a magnetic field. The coercive force and squareness ratio of the oriented sheets were 412 kA m(-1) and 0.91, respectively. The magnetic anisotropy field was determined by measuring the rotational hysteresis losses of the oriented sheets with a magnetic torque meter. The anisotropy field was distributed in the range of approximately 200-1100 kA m(-1), and particles with an anisotropy field of 478 kA m(-1) comprised the majority. The magnetic anisotropy energy estimated from the magnetic anisotropy field was 104 KJ m(-3). Assuming a reduction in the crystalline anisotropy field along the c-axis due to simply the shape anisotropy field resulting from the platelet shape of the particles, particles occupying the majority exhibited a maximum anisotropy field of 823 kA m(-1).