MICROMAGNETIC SIMULATIONS AND APPLICATIONS

Fast and coherent switching of small magnetic nanoparticles forms the basis of many modern magnetic devices such as ultra high magnetic storage media and precise magnetic sensors. The transition from uniform to nonuniform magnetization reversal modes is described analyzing the change of the total energy with the external field. The dynamic response of the magnetization follows from the Gilbert equation of motion which is solved numerically using a finite element method. Examples of dynamic magnetization processes are given for magnetic nanostructures as used in discrete storage media and magnetic field sensors. Both, the switching field and the switching time of Co-nanoelements decrease with increasing surface roughness of the nanostructures. In square NiFe elements two different reversal modes are observed in the simulations, depending on the domain structure for zero applied field. The field required to switch the magnetization of the C-state is about twice as large as the switching field of the S-state. Adaptive meshing is used to calculate domain wall motion in magnetic nanowires. The domain wall structure changes from a transverse wall to a vortex wall the wire diameter is increased from 20 nm to 40 nm. For a given external field, the vortex wall moves faster than the transverse wall, reaching a domain wall velocity in the order of 1000 m/s.