Modeling of elongated fine ferromagnetic particles

Abstract

This paper presents some results of a numerical micromagnetic calculation for ferromagnetic fine particles. Two basic shapes are discussed: elongated parallelopipeds and parallelopipeds with pointed ends. The variation of coercivity, switching field, and reversal modes with particle size, orientation, and material parameters are discussed. Equilibrium magnetization structures suggest that particles may have remanent states that are substantially nonuniform. The flipping mode, in which the magnetization reversal starts from the longitudinal ends of the particles, is found to be the energetically favorable switching mechanism. Small particles are switched by the quasi-coherent flipping mode, while large particles are reversed by the quasi-curling flipping mode. The angular dependence of the coercive and switching fields for three particle sizes is found to agree qualitatively with classical results, but both fields are quantitatively smaller. The nucleation field is compared with the Stoner–Wohlfarth model as well as with the curling mode, and is found to be about half of their value.