Modelling of magnetisation reversal in thin films, nanodots, nanopillars and nanowires

Magnetic nanostructures have attracted attention due to their possible applications in information storage and sensors. The switching time and switching field are two magnetic properties that can determine the applicability of magnetic nanostructures. It is known that changing the composition or geometry of a magnetic nanostructure can change its switching time and switching field. Geometry can be changed by the addition of artificial structuring. However, complete control of these parameters has not yet been achieved. To investigate the changes in switching time and in switching field, the magnetisation reversal of nanostructures containing various compositional changes and various artifcially introduced structures were modelled. It is observed in Ni80Fe20 nanowires of diameter 100 nm that are switched by an external magnetic field of 25 kAm-1, switching time increases when the damping parameter is increased from 0.0861 to 0.5. Whereas, for an external magnetic field of 250 kA m-1, switching time decreases as the damping parameter is increased from 0.0861 to 0.18. Increasing the damping parameter, from 0.18 to 0.5, increases the switching time. When a spherical artificial structure is introduced along the length of the nanowire, the position of the spherical artificial structure relative to the longitudinal axis of the nanowires was found to a ect the switching time for external magnetic fields of 30 kA m-1 and 250 kA m-1. In an external magnetic eld of 30 kA m-1, the switching time peaks when the spherical arti cial structure is placed halfway along the longitudinal axis of the Ni80Fe20 nanowire. Whereas in an external magnetic eld of 250 kA m-1, the switching time is at a minimum when the spherical artificial structure is placed in the same position. For the hemispherical arti cial structures at the end of the Ni80Fe20 nanowire, the switching time increases when the length of the hemispherical artificial structure is increased. Due to computational limitiations, the effect of interaction in nanowires on the switching time is di cult to investigate. Thus, previous research on this topic in nanowires and in nanostructures containing artificial structures has usually been performed on isolated structures. To determine if interacting nanowires that contain artificial structures affect the switching time, arrays of Ni80Fe20 nanowires were modelled. Observed in arrays of Ni80Fe20 nanowires that contain various arti cial structures, the switching time generally decreases as the number of interacting nanowires are increased. The objective of achieving faster switching times has been met. Research shows that increasing the rare-earth doping of Ni80Fe20 nanowires can decrease the switching time at large magnitudes of external magnetic elds and low values of the damping parameter. A possible new observation is seen in the investigation of introducing artificial structures where the addition of a spherical one in the middle of the nanowire can decrease the switching time at large magnitudes of external magnetic field. Rounding the ends of the nanowire could also decrease the switching time.