Applications of Multi-scale Modeling to Spin Dynamics in Spintronics Devices

Abstract

The design of modern spintronic applications relies on the accurate simulation of nanomagnetic structures in realistic situations. Simulations can be particularly challenging when they need to consider effects that unfold on vastly different length scales. Multiscale modeling techniques are a powerful way to treat such cases, especially when the different length scales are coupled, such that the coarse length scale cannot be modeled without considering the fine scale or vice versa. This chapter discusses various approaches and features of multiscale simulations of the magnetization in micro- and nanomagnetism. It gives an overview of numerical techniques used in this scientific domain to bridge different length scales and discusses recent multiscale studies in three-dimensional nanomagnetism. The transition to three dimensions that is currently occurring in nanomagnetic research entails new challenges for the modeling of the magnetization. One of the reasons is the occurrence of Bloch points, as three-dimensional magnetic switching processes often involve the nucleation and propagation of these singularities of the magnetization field. Bloch points are three-dimensional magnetization structures that extend over several tens of nanometers and which require an atomistic treatment of their core region. Fully dynamic micromagnetic multiscale simulations with atomistic-continuum coupling have recently been used to simulate the field-driven motion of Bloch points. The transfer of multiscale modeling known from other domains of material science to the simulation of magnetic structures has made it possible to perform numerical studies providing insight into the structure and dynamics of Bloch points and their interaction with the atomic lattice.