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|Title: ||A study of superconductivity in single crystals and thin films using muon-spin rotation and neutron scattering|
|Authors: ||Heron, David Owen Goudie|
|Supervisors: ||Lee, Stephen|
|Issue Date: ||2009|
|Abstract: ||The archetypal high temperature superconductor Bi₂Sr₂CaCu₂O[subscript[8+δ]] has been extensively investigated. However, until now, little has been known about the behaviour of the
magnetic vortices inside the Vortex Glass and liquid state. µSR measurements have shown
a negative skewness for the field probability distributions in these regimes. Such a negative
skewness has only recently been explained as being a direct consequence of three-body correlations between vortices in a similar layered superconductor. With a new understanding
and knowledge of the physics of these systems, it is instructive to re-visit the superconductor Bi₂Sr₂CaCu₂O[subscript[8+δ]] to explain the evolution of these three-body correlations occurring here.
Comparing this with the ion-irradiated superconductors (of the same Bi₂Sr₂CaCu₂O[subscript[8+δ]] material), allows one to observe how three-body correlations between vortices evolve differently to that in the pristine material. Moreover, in the region of the macroscopic irreversibility
line, entropically driven disorder exists below the matching field B[subscript[ϕ]] , whilst there is the appearance of relatively straight vortex lines at fields above B[subscript[ϕ]] . Such phenomena suggest a
significant di fference in the evolution of three-body correlations compared with the unirradiated material.
There has been much work conducted on the interplay between superconductivity
and magnetism in materials of reduced dimensions. Work presented here on the ferromagnet/superconductor trilayer system (Permalloy/Nb/Permalloy) has shown a novel magnetic
profile at the interface between the ferromagnetic and superconducting boundary, where,
contrary to what is expected, the magnetism appears to be significantly suppressed at the
interface before increasing towards the centre of the Nb layer.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Physics & Astronomy Theses|
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