Magnetization processes in small ferromagnetic particles with inhomogeneous demagnetizing field and uniaxial anisotropy

Abstract A numerical micromagnetic method was used to calculate the magnetization processes in small rectangular parallelepipeds with uniaxial crystalline anisotropy and inhomogeneous demagnetizing fields. With the material parameters of the Fe 14 Nd 2 B phase the temperature dependence of the nucleation field was calculated for a particle size of 10 μm. The microstructural parameters describing the nucleation field were determined. They are in excellent agreement with measurements on Fe 14 Nd 2 B sintered magnets. The stable remanent state was calculated for different ratios of the anisotropy and the magnetostatic energy for arbitrary materials. The critical radius for single domain particles was determined by comparing the stable equilibrium states. The demagnetization curve for particles with low and high crystalline anisotropy compared to the stray field energy were calculated. The crossover from hard magnetic to soft magnetic behavior was investigated. The shape of the demagnetization curve as well as the coercivity changes drastically.