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Highly time-resolved single event capture of field- and current-induced magnetization dynamics in thin metallic films and nanostructures

Final Activity Report Summary - SINGLE MAGN DYNAMICS (Highly time-resolved single event capture of field- and current-induced magnetisation dynamics in thin metallic films and nanostructures)

The objectives of this project were to build a microscope for capturing the motion of domain walls in magnetic nanowires in a single exposure ("single shot measurement"), and use it to study magnetic field- and electric current-induced domain wall motion in the wires. Achievements in the area of the experimental set-up included optics for focusing the microscope laser beam to a diameter of one micrometre, a precise sample scanning system for positioning the laser beam on a magnetic nanowire, and a custom built high frequency electromagnet to function together with the above. Techniques were developed to measure the laser beam diameter, automatically position domain walls in the magnetic nanowire, and importantly, to record the trace of the domain wall motion in a single shot.

Scientific achievements included the measurement of magnetic field-induced domain wall velocities in nickel-iron alloy (Permalloy) nanowires and in Permalloy wires containing small amounts of holmium. The holmium was shown to decrease the domain wall velocity, and simulations indicated that this is accompanied by changes in the domain wall structure during the propagation. Since the measurements were single shot, a study was also permitted of the characteristic random behaviour of the domain wall motion due to temperature effects and natural inhomogeneities in the sample. Current-induced domain wall velocities in the Permalloy wires did not change with increasing holmium content, in contrast to domain walls propagated by field. This is the most important scientific achievement of the project; it allows a test of theories of current-induced magnetisation switching and it contributes to the understanding of the interaction between electric current and magnetic domain walls.