Date Awarded

2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physics

Advisor

R Ale Lukaszew

Abstract

This dissertation presents various investigations into the structure-property correlations in highly anisotropic FePt and FePd thin films and nanostructures. These binary alloy thin films may exhibit long-range chemical ordering (e.g. L10), which induces a strong uniaxial magnetic anisotropy whose orientation is dependent on the ordering direction in the thin film. The chemical ordering, and hence the magnetic anisotropy, in these thin films can be controlled and tailored through sputter deposition and ion implantation conditions followed by subsequent processing. Two novel fabrication methods, x-ray rapid thermal annealing (XRTA) and heavy ion implantation, successfully demonstrate the ability to obtain highly anisotropic nanometer-sized L10 ordered regions in thin films. XRTA has the advantage of using high brilliance x-ray undulator radiation to simultaneously induce and probe microstructural changes in real time and is shown to favorably modify the chemical order in partially-ordered FePt thin films without affecting the average ordered grain size. Heavy ion implantation has the advantage of fabricating nonequilibrium nanocomposite thin films, which in the case of Fe+ implanted Pt thin films requires lower activation energies to nucleate and grow the L10 phase thus implying lower processing temperatures. The magnetic anisotropy in these binary alloy thin films is not only tailored through the chemical ordering, but can be further influenced by an adequate choice of the capping layer. Magnetically polarizable capping layers (e.g. Pd) decrease the perpendicular magnetic anisotropy (PMA) of FePd thin films, while non-polarizable capping layers (e.g. MgO) have no effect on the PMA. Different magnetization profiles of the films obtained from x-ray resonant magnetic scattering measurements explain this change observed in the magnetic anisotropy. The magnetic domain structure in these highly anisotropic thin films is also important and influenced by the magnetic anisotropy. An analytical model shows good quantitative agreement with experiment for FePd thin films above a critical thickness, thus showing the direct correlations between chemical order, magnetic anisotropy, and magnetic domain structure in these films.

DOI

https://dx.doi.org/doi:10.21220/s2-kae4-ca25

Rights

© The Author

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