In this thesis the structural and magnetic properties of two epitaxial heterostructures, Co<sub>75</sub>Fe<sub>25</sub>/Cu(110) and Co/Cu(311), are presented. The initial stages of growth are investigated, along with their interaction with gaseous adsorbates and overlayers. Furthermore, MgO is grown and studied for use as a tunnel barrier. For the growth of Co<sub>75</sub>Fe<sub>25</sub>/Cu(110) a 2D percolation magnetic phase transition is observed with a critical exponent γ = 2.385 ± 0.069, in excellent agreement with the theoretical value γ = 2.389. The changing ratio of the in-plane cubic and uniaxial anisotropy with film thickness leads to a rotation of the in-plane magnetic anisotropy. This rotation can be reversed by the addition of a submonolayer Cu overlayer. Dosing the system with oxygen revealed three distinct regions in the evolution of the coercive field: a decrease in the coercive field (I), the formation of a distinct peak (II), and a steady increase in the coercive field (III). The effect of dosing with hydrogen is qualitatively similar, although the observed features are generally less pronounced. In contrast to the CoFe/Cu(110) system for Co/Cu(311), a purely uniaxial magnetic anisotropy was observed for films of up to 15 ML; hence no rotation of the magnetic easy axis was observed. What is more, the results suggest a 3D not 2D phase transition.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598739 |
| Date | January 2009 |
| Creators | Easton, S. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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