On the computation of particle demagnetizing fields

The nonuniform demagnetizing fields of a magnetic particle are computed. It is shown that the dipole-dipole approximation introduces large errors only for the nearest neighboring elements, and they can be corrected by numerical integration over the surface charge of each element. The coercivity and the squareness ratio are calculated as functions of the particle aspect ratio and width. The coercivity is found to saturate at a smaller aspect ratio than that of the ideal spheroids. The remanent magnetization transforms from a uniform state to a vortex state at a characteristic particle width regardless of the particle length. However, longer particles have higher squareness ratios.>