Computer simulation study of dynamics and domain structures in different magnetic systems

Spin wave modes in Permalloy stripes with transverse applied field were studied both by micromagnetic simulations and by solving the linearized equation of motion. In high field regime, localized spin wave modes are observed. In low field regime, crossover spin wave modes of mixed Damon-Eshbach and backward volume character are observed. The lowest frequency localized modes completely soften when the magnetization is saturated at very high external field.;The hysteresis loops in both easy and hard axes are calculated in simulations for a FeCo thin film rectangle. The reversal process in the easy axis is studied by applying a tipping pulse. With a large applied field in the easy axis, two resonance modes are observed. The higher frequency mode is concentrated at the central part of the rectangle while the lower frequency one is located at the corners. For a Permalloy thin film square, spin wave modes excited from the Kittel structure were studied. Systematic but complex spin wave modes are observed.;Unconventional two dimensional magnetic vortex structures, which have the same exchange energy and surface charge density but different volume charge density compared to the conventional vortex structures, are observed at the cross-section area of two Permalloy thin film wires in simulations. Isolated anti-vortex structures are also observed in the same geometry but with a different initial condition.;Logic gates are designed using magnetic elements through magnetostatic interaction. Two setups can operate the AND function in simulations.;The effect on the magnetization of the magnetic field produced by the electric current passing through the magnetic sample were studied in simulations. The circular field due to the electric current may cause a vortex structure or even change the chirality of the vortex depending on the current density, the material and size of the sample.