| Periodic boundary conditions (PBCs) are a useful concept in many areas of physics. In micromagnetic simulations they allow efficient modelling of highly regular periodic magnetic structures. However, it'not easy to implement PBC in micromagnetic because the demagnetization interaction have a long-range character and it's not reasonable to introduce a cutoff radius due to its quite slow decay. Therefore, Lebecki et al. described PBC for one-dimensional case in detail. A method based on K.M. Lebecki's work was put forward here for the situation of two-dimensional periodic boundary conditions (2D PBC):discrete infinity summation of demagnetization tensors was approached by a con-tinuous integration without any range cutoff. The demagnetization field for 2D PBC was calculated by recombining the demagnetization tensors, for which fast Fourier Trans-form (FFT) algorithm can be applied to accelerate the computation. The method was implemented in the publicly full micromagnetic package (OOMMF) by replacing the normal demagnetization tensor in real space with the assembled demagnetization ten-sors that have to be evaluated only once at the beginning of the simulations.Magnetic domain wall motion in nanowire (such as induced by spin-polarized elec-tric currents) has attracted significant interests recently due to its potential applications. However, we want to neglect the effect caused by the finite length of the nanowire in most cases when the domain wall dynamics are studied using the micromagnetic sim-ulations. Thus, we implement the two-dimensional infinite boundary conditions (IBC) in OOMMF.Although the dynamics of the magnetic sample only with the uniaxial anisotropy under the applied field have been well studied, the elliptical thin film magnetic sample havn't because the easy-plane anisotropy breaks the rotational symmetry which will ca-sue the magnetization motion are complex. In order to simple the analysis the elliptical thin film magnetic sample were considered with a strong easy-plane anisotropy and a weaker uniaxial anisotropy. The the perturbation method can be performed to chase the minimal switching field, and the trajectory of fastest magnetization switching was given. The system under circularly-polarized microwave was also researched, which showed the result that the frequency of FMR will decrease with the increasing of amplitude of microwave. |
