Magnetization Dynamics In Magnetic Nanostructure

The springing up of the direction of magnetic dynamics issues has attracted extensively attention in spintronics recently. To understand and control the magnetic moment reversal in magnetic materials possesses alluring prospects in reality electronic and information industry manufacture. Moreover, understanding comprehensively the reversal mechanism could provide theoretical guidance to actualize high-density and ultrafast reading-writing information magnetic storage device no matter in device specimen fabrication or information data processing. Nevertheless, due to the complexity of magnetic moment reversal in reality magnetic materials, there are always some new phenomena in the fields of single domain and magnetic domain wall. Therefore, we have to obtain further more knowledge and understandings to explain the observed phenomena.In the paper, we mainly investigate magnetic nanoparticles and the notched domain wall in ferromagnetic nanowires to illustrate some problems in magnetization reversal with the aid of magnetic simulation software OOMMF.First, we have discussed the reversal of magnetic nanoparticle in presence of external magnetic field in consideration of different particles with different materials and sizes. The dynamics can be described by the Landau-Lifshitz-Gilbert equation in reversal process. It was found that the switching field decreases considerably as particle size increases for single domain particles. Furthermore, there exist two different reversal modes, uniform and non-uniform from the numerical simulation and the critical edge length was found for the transition between the two modes. Then we can attempt to control the reversal of part of particles in presence of magnetic field.Second, magnetization reversal of two-body stoner particles with dipolar-dipolar interaction are discussed with different fixed distance between two particles. It was foundthat there exists a minimum switching field when the magnitude of inter-particle distance decreases to a certain value in perpendicular configuration. And then we can apply this conclusion to utilize magnetization reversal for two single-domain particles with minimum cost and energy consumption.The final part of the paper shows the pinning effect of the notched domain wall in ferromagnetic nanowires in presence of external field. In this work, we have investigated numerically with the OOMMF software the relationship between the pinning field and the notch size and relative positions in nanowires. It was shown that the pinning field of domain wall increases as the notch length increases and decreases as the notch width increases. We also found that the pinning field is lowest when the notch is located in the middle along the nanowire width for domain walls with two kinds of chirality. We believe that the obtained conclusion could be useful in future storage devices with internal stress or artificial defects.