Ferromagnetic Line Width of Nonoriented Polycrystalline Hexagonal Ferrites with Large Magnetic Anisotropy Fields (Correspondence)

Data on the line widths of oriented polycrystalline, hexagonal ferrites with large magnetic anisotropy fields have shown that the uniaxial ferrites (easy direction of magnetization along the C axis) have a considerably larger line width than that of planar ferrites (easy plane of magnetization perpendicular to the C axis). For example, in work performed at Philips on the uniaxial barium and strontium ferrites of the magnetoplumbite structure, with aluminum or titanium-cobalt substitutions, the line width varied over a range of 1600 to 3300 oersteds for materials with anisotropies ranging from 7000 to 52,000 oersteds. There was no strong correlation between line width and anisotropy field. In work done at Sperry on uniaxial nickel-W compounds with cobalt substitutions, the line width ranged from 2200 to 3000 oersteds for materials with anisotropies ranging from 7000 to 12,800 oersteds. On the other hand, in work performed by RCA on planar ferrites, a line width as low as 110 oersteds was obtained, and a large number of compounds had a line width less than 500 oersteds.