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Title: The growth of ultra-thin magnetic films and the effects of gaseous adsorbates
Author: Easton, S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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In this thesis the structural and magnetic properties of two epitaxial heterostructures, Co75Fe25/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 Co75Fe25/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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available