Ab‐Initio Real‐Time Magnon Dynamics in Ferromagnetic and Ferrimagnetic Systems

Abstract

Magnonics—an emerging field of physics—is based on the collective excitations of ordered spins called spin waves. These low‐energy excitations carry pure spin currents, paving the way for future technological devices working at low energies and on ultrafast timescales. The traditional ab‐initio approach to predict these spin‐wave energies is based on linear‐response time‐dependent density functional theory (LR‐TDDFT) in the momentum and frequency regime. Herein, the simulation of magnon dynamics using real‐time time‐dependent density functional theory is demonstrated, thus extending the domain of ab‐initio magnonic studies. Unlike LR‐TDDFT, this enables us to observe atom‐resolved dynamics of individual magnon modes and, using a supercell approach, the dynamics of several magnon modes can be observed simultaneously. The energies of these magnon modes are concurrent with those found using LR‐TDDFT. Next, the complex dynamics of the superposition of magnon modes is studied, before finally studying the element‐resolved modes in multisublattice magnetic systems.