Regensburg 2022 – wissenschaftliches Programm
MA 17.1: Hauptvortrag
Dienstag, 6. September 2022, 15:00–15:30, H43
Ultimately fast, small and energy-efficient magnetism: fundamentals and prospects — •Johan Mentink — Radboud University, Nijmegen, The Netherlands
Findings ways to switch between magnetically ordered states at the smallest possible length and time scale, while simultaneously dissipating the least amount of energy is a major challenge in magnetism. One of the most appealing routes to achieve this goal is by bringing a magnetic system strongly out of equilibrium, after which the dynamics is driven by exchange interaction, the strongest force in magnetism. Although this has been extensively discussed in ferrimagnetic systems, harnessing such exchange-driven dynamics in ferromagnets is fundamentally limited by angular momentum conservation. We will discuss basic models of magnetism that can be solved even under strongly nonequilibrium conditions and have been key to identify the mechanisms for ultrafast switching. We will exemplify this for chiral ferromagnets as studied by recent XFEL experiments. For this case, the nonequilibrium dynamics is driven by an additional antisymmetric exchange interaction, resulting in ultrafast nucleation of nanoscale magnetic skyrmions. This opens a new path for switching that is not only fast, but also can operate at the nanoscale. By comparing with the fundamental energy-speed limits for switching between physically distinct states, we will argue that such exchange-driven dynamics can be key to achieve even faster, smaller and much more energy-efficient switching than demonstrated so far.