Cylindrical domains in small ferromagnetic spheres with cubic anisotropy

Magnetization configurations are computed for small ferromagnetic spheres with cubic anisotropy. A cylindrically symmetrical configuration is found, which has a lower energy than a single domain, for a sphere radius larger than about 27.7 nm, for cubic cobalt. In magnetite, the changeover from a single domain to the cylindrical configuration is at a radius of about 27.0 nm. This problem has been studied particularly for cubic iron oxides, used in magnetic recording.