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Ultrathin magnetic films are now vital components in many everyday devices, such as computer hard drives and memory. As the need for smaller, faster and more sensitive devices becomes more necessary, the need to understand and control the behaviour of these films becomes more essential. This research proposal presents an opportunity to investigate a range of smart magnetic materials, which are ideal for practical applications. Smart materials have high magnetostriction constants, which mean they change length when placed in a magnetic field. This property can be utilised, so that the films can act as switches or sensors. One problem with these materials is that they have a too wide hysteresis loop at zero field, i.e. a large coercivity. Therefore, to improve the usefulness of these smart materials, their magnetostriction must be increased, while decreasing their coercivity. This research proposal aims to investigate how different fabrication techniques change the magnetic properties and microstructure of smart materials such as the alloys FeCo and Fe-Ga. In doing this produce ultrathin magnetic films which have larger magnetostriction constants, but smaller coercive fields than previous work has achieved. The research focuses on two areas, the first is the controlling of the magnetic properties of FeCo ultrathin films, and the second is the fabrication of the novel magnetic alloys Fe-Ga and FeCo-Ga into thin films. FeCo has the second highest magnetostriction constant, for an alloy containing no rare earth elements, (Fe-Ga has the highest magnetostriction constant.) They are therefore ideal to investigate to determine, whether it is possible to control the film growth, so that the film's magnetostriction constant increases, and the coercivity decreases. Bulk Fe-Ga was discovered in 1998, and has the ideal properties required for smart magnetic thin films. This project aims to be one of the first to fabricate Fe-Ga into thin films. The FeCo films will be grown in the state-of-the-art Kurt J Lesker deposition system at Sheffield University. The deposition system allows different fabrication techniques to be carried out during the dc sputtering of the FeCo. These include heating and rotating the substrate, and applying a magnetic field during growth. These techniques will be undertaken to determine how they change the magnetostriction and coercivity of the FeCo films. The Fe-Ga films will be grown in a slightly different way, due to the low melting point of the Ga. A specially designed fabrication chamber will be used to fabricate the films, where the Fe is dc sputtered at the same time that the Ga is evaporated. Once the fabrication procedure of Fe-Ga films has been established, then the techniques used to optimise the FeCo films properties will be carried out on the Fe-Ga films, so to optimised their properties. For all the magnetic films, the magnetisation, the magnetoresistance and the microstructure will be studied. The magnetisation and magnetoresistance will be measured as function of strain, as this allows the magnetostriction constant to be determined. The microstructure will be studied using electron microscopy. The changes in all these properties will be investigated for each technique; hence a comprehensive study of how these smart magnetic materials are affected by different fabrication techniques will be established. This will help to optimise the properties of these magnetic materials in thin film form, to be used in practical applications.In conclusion this research proposal presents the opportunity to provide a complete study of smart magnetic materials, including how their magnetic and electrical properties change for different fabrication techniques, and the fabrication of the new alloy Fe-Ga into thin films.
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