Micromagnetic Simulation of Switching Mechanism in Permalloy Square Rings

We demonstrate how the micro magnetic simulations could reproduce the experimentally found onion, horseshoe, and vortex configurations in square ring nano-magnets for different field orientations. Then we discuss an existence of a less known intermediate state which consists of two domain walls along one side of the square ring and how the annihilation of those two domain walls leads to the formation of a vortex state for the external field applied parallel to the square rings. Finally we compare our simulations with results of Lorentz Microscopy. Reliable simulation is the key for the implementation of magnetic square rings as memory elements and inputs for magnetic logic gates.