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The interplay of magnetism and structure in patterned multilayer thin films
CJ Kinane (STFC Rutherford Appleton Lab.) (Pr.Au.)
This thesis contains three studies on artificially roughened multilayers, with the aim of investigating how the structural disorder affects the magnetic structure. The magnetically patterned system uses a Co/Pt multilayer, which exhibits strong perpendicular magnetic anisotropy, to magneto statically imprint a domain pattern onto a 50 Å thick permalloy layer. Element specific SXRMS experiments were then performed. Off-specular magnetic satellite peaks, corresponding to a periodic domain stripe width of 270 nm, were observed, confirmed by magnetic force microscopy and micromagnetic modelling. Thus, we have exploited the element specificity of SXRMS to discern the purely magnetic correlations in a structurally flat permalloy film. The next step was to structurally and magnetically roughen a magnetic system and use PNR to provide a reference to help separate the structural and magnetic contributions in the SXRMS. In this case, nanospheres were used to pattern a Co/ Pt multilayer into nanopillars. On top of this was deposited a Co/Ru multilayer, which was AF coupled. The SXRMS showed how the magnetic roughness correlates with the structural roughness. We saw that the magnetic disorder was similar over a range of length scales out as far as 15 µm. In addition, the PNR data indicated that the domain reversal was facilitated by domain nucleation. Finally, by introducing a solid solution at the interface of an AF coupled multilayer we have demonstrated a temperature controlled variation of the interlayer exchange interaction. The AF scattering is observed at room temperature and is maintained as the system is cooled down to 10K. However the AF correlations are destroyed upon magnetically saturating the system and are not recovered upon field cycling. The AF correlations reappear at about 150 K upon warming. A similar effect at low temperature was also seen in VSM measurements, however no mechanism for the observed effect could be determined.
Polarised neutron reflectivity
Soft x-ray reflectivity
RAL-TH-2008-001. PhD, Univeristy of Leeds, 2008.
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