Abstract
We investigated systematically the easy axis magnetization reversal of 20 nm thick permalloy ellipses with a fixed major axis of 1.47 µm and minor axes of 0.22�1.47 µm. Lorentz transmission electron microscopy was used to image the micromagnetic configurations during magnetization reversal. Hysteresis loops of single ellipses were recorded by means of micro- Hall magnetometry and could be ...
Abstract
We investigated systematically the easy axis magnetization reversal of 20 nm thick permalloy ellipses with a fixed major axis of 1.47 µm and minor axes of 0.22�1.47 µm. Lorentz transmission electron microscopy was used to image the micromagnetic configurations during magnetization reversal. Hysteresis loops of single ellipses were recorded by means of micro- Hall magnetometry and could be traced back to certain reversal mechanisms observed by Lorentz microscopy. In most cases, the magnetization reversal is initiated by the evolution of a magnetization buckling, followed by the formation of a single, a double, or a trapped vortex configuration. For ellipses with high aspect ratio (length- to-width ratio), the magnetization switches in the reversed magnetic field without creation of a stable vortex configuration. Our experiments show that the characteristic field values for vortex creation, single vortex annihilation, and switching strongly depend on the shape anisotropy of the elements.
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