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Neutron scattering and muon-spin rotation studies of superconducting materials
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dc.contributor.advisor | Lee, Stephen Leslie | en |
dc.contributor.author | Drew, Alan J. | en |
dc.coverage.spatial | xxii, 279 p : ill. (some col.) 30 cm. | en |
dc.date.accessioned | 2021-04-08T08:45:35Z | |
dc.date.available | 2021-04-08T08:45:35Z | |
dc.date.issued | 2005 | |
dc.identifier.uri | https://hdl.handle.net/10023/21808 | |
dc.description.abstract | Small angle neutron scattering (SANS), muon spin rotation (μSR) and associated characterisation techniques have been used to measure novel properties of supercon¬ ducting materials. The coexistence of Type-I and Type-II behaviour in LaNiSn has been observed using μSR and the thermodynamic phase boundary has been identified between this behaviour and that of a conventional Type-I superconductor. In a zero field cooled state the existence of a pure Meissner state is observed only at this thermodynamic phase boundary. The magnetic phase diagram of the high temperature superconductor La. ₁.₈₃Sr₀.₁₇ CuO₄ has been investigated. SANS has provided the first microscopic observation of a vortex lattice and the first unambiguous evidence for a field induced hexagonal to square vortex lattice structural transition in the high temperature superconductors. This is supported by μSR measurements, which also yield information on vortex lattice pinning and the melting transition. A preliminary SANS experiment on La₁.₉Sr₀.₁CuO₄ at low fields suggests a Bragg glass (BG) with nominally a hexagonal structure. μSR has provided unambiguous evidence for a field induced crossover from a BG to a more disordered vortex glass (VG) state and an upper limit on the crossover field is given. This is the first measurement of a disordered VG state on a system of well coupled vortex lines. Furthermore, a study of the evolution of short range order is presented that is of universal significance, as it provides experimental insights into space averaged many particle correlations in bulk systems. Direct evidence for the coexistence of a spin density wave (SDW) with bulk superconductivity in a Ferromagnetic/Superconducting/Ferromagnetic trilayer has been obtained using low energy μSR. The apparent enhancement of the SDW amplitude in the superconducting state and the π/2 phase shift of one component of the SDW below Tc indicates a profound coupling of these two forms of spin order. | en |
dc.language.iso | en | en |
dc.publisher | University of St Andrews | en |
dc.subject.lcc | QC611.95D8 | |
dc.subject.lcsh | Superconductors | en |
dc.subject.lcsh | Neutrons--Scattering | en |
dc.subject.lcsh | Muon spin rotation | en |
dc.title | Neutron scattering and muon-spin rotation studies of superconducting materials | en |
dc.type | Thesis | en |
dc.type.qualificationlevel | Doctoral | en |
dc.type.qualificationname | PhD Doctor of Philosopy | en |
dc.publisher.institution | The University of St Andrews | en |
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