Micromagnetic modeling of the polycrystalline structure effect to the hysteresis loop in ferromagnetic nanowire

Extensive micromagnetic simulation results of the hysteresis loops in ferromagnetic nanowire with randomly oriented crystallites ordered in one chain is presented. Three main contributions to the magnetic energy of the wire had been taken into account: exchange, dipole-dipole, and the magnetic anisotropy energy of the crystallite. In cases where one of the three contributions to the energy can be neglected, the numerical calculations are in good agreement with the results of the well-known, analytically studied micromagnetic problems. In the case when all three contributions are comparable, a complex non-monotonic dependence of the coercive force on the crystallite size and the magnetic anisotropy constant is observed. In order to interpret these changes, a new micromagnetic scale is introduced, which takes into account all three contributions to the magnetic energy of the wire, and performs a correct transition to the analytically studied limits, which take into account the competition of any two contributions. (paper)