| Summary: | Until the last few years, focussed ion beam systems were primarily used within the semiconductor industry as tools for modifying prototype integrated circuits, but owing to the development of commercial systems and the concomitant reduction in costs, they are rapidly becoming more popular within academic institutions for research purposes. This work investigates the potential application of the focussed ion beam to the study of patterned magnetic media, which is an area of increasing interest as new methods of extending the performance limits of current magnetic storage media are sought. The effects of quasihomogeneous Ga ion implantation and micro-machining on the structural properties and magnetic behaviour of thin Fe films have been studied by various microscopy techniques. Doses on the order of 8 X 10 15 ions cm"2 were found to induce structural changes in the polycrystalline microstructure, but the ferromagnetic properties were found to be reasonably resistant to ion implantation. The formation of magnetic domains within patterned arrays of simple geometric shapes was studied using magnetic transmission X-ray microscopy and Xray magnetic circular dichroism. Hysteresis properties of the patterns were determined by magneto-optical measurements using a specially designed dual photoelastic modulator-based polarimeter. A detailed description of the polarimeter is given along with a new calibration method, which improved the accuracy of the measurement system in comparison to a more conventional approach.
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