Hysteresis and switching dynamics of patterned magnetic elements

The hystersis properties and the switching time of Co-nanoelements were calculated using finite element micromagnetics. The calculated coercive field of 200x40x25 nm Co-nanoelements strongly depends on the model of the polycrystalline microstructure assumed in the simulations. For small, randomly oriented grains the magneto-crystalline anisotropy may be neglected, since the effective anisotropy vanishes due to averaging. Quasistatic simulations of magnetization reversal show that taking anisotropy into account favors the formation of vortices and therefore reduces the coercive field from 140 kA/m to 95 kA/m. Vortices immediately form after the application of an reversed field, assuming a polycrystalline microstructure. For an applied field close to the coercive field, vortices form only after after a certain waiting time