Micromagnetic Simulations on GPU, A Case Study: Vortex Core Switching by High-Frequency Magnetic Fields

Since magnetic vortex cores have two ground states, they are candidates for digital memory bits in future magnetic random access memory (MRAM) devices. Vortex core switching can be induced by exciting the gyrotropic eigenmode, e.g., by applying cyclic magnetic helds with typically a sub-gigahertz frequency. However, recent studies reveal that other modes exist that can be excited at higher frequencies, but still lead to switching with relatively small held amplitudes. Here, we perform a full scan of the frequency/amplitude parameter space to explore such excitation modes. The enormous amount of simulations can only be performed in an acceptable time span when the micromagnetic (CPU) simulations are drastically accelerated. To this aim, we developed MUMAX, a GPU-based software tool that speeds up micromagnetic simulations with about two orders of magnitude compared to standard CPU micromagnetic tools. By exploiting MUMAX's numerical power we were able to explore new switching opportunities at moderate held amplitudes in the frequency range between 5 and 12 GHz.