Estudo da dinâmica da parede de domínio transversal em nanofitas magnéticas na presença de impurezas

Abstract

The study of the dynamics of domain wall in magnetic nanowires have attracted a vast interest because of their important technological applications in magnetic media and MRAM’s (Random Access Memory). For certain geometries and sizes, magnetic nanowires present transverse domain walls or vortex domain walls, which with the application of an ex-ternal field can be transported to different regions of the nanowire without losing its magnetic properties. In this work, we have studied the influence of a cluster of magnetic impurities on the transverse domain wall (TDW) dynamics in a magnetic nanowires of Permalloy-79 (Ni79Fe21) using numerical simulations. The TDW is driven by the application of a spin polarized current in the direction of the nanowires axes. In our simulations, the nanowires are modeled by a Hamiltonian that takes into account the short (exchange) and long (dipolar) range interactions of magnetic moments. The dynamics of the system is governed by the Landau-Lifshitz-Gilbert equations with spin current term. We have studied the interaction potential between the TDW and the cluster, and by varying the applied spin current, we can determine the minimum value of the current necessary to depin the domain wall of the cluster. We have shown that this minimum value depends on the width of the nanowire and the exchange constant J' between the material of the nanowire and the impurity. The present study is of the great significance for technological applications that use movement of domain walls.