Material requirements for circular magnetic domain devices

The material requirements of circular cylindrical domain devices are discussed. The current status of the search for circular domain materials is summarized with respect to the anisotropy field Hkand the saturation magnetization Msby a chart showing the influence of these quantities on the size, stability and mobility of the circular domains. A preferred region is defined on the chart and representative materials are plotted. At the present time, the preferred region is most closely approached by certain mixed rare-earth orthoferrites and the aluminum substituted hexagonal ferrites.