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UBC Theses and Dissertations

Microwave studies of high temperature superconductors : extraction of absolute magnetic penetration depth of cuprate superconductors from underdoped to overdoped Mullins, Geoffrey Kale


The London Penetration depth, and complex conductivity of Tl2Ba2Cu3O6+δ and YBa2Cu3O6+δ were measured at microwave frequencies using a loop gap resonator. A theoretical description of cavity perturbation analysis is given with emphasis assumptions of the model. The experimental apparatus is described, both in design and function, and a discussion is given of the difficulties associated with environmental conditions under which these measurements are made. The extraction of electronic properties from measured quantities is explained for the samples of Tl2Ba2Cu3O6+δ, that go into the thin limit regime. These properties can be understood through a model which is based on incoherent, quasipartieal hopping between superconducting planes. Differences in the material properties between pure, and gadolinium doped, YBa2Cu3O6+δ are accounted for by examining the properties of a dilute spin system. Measurements taken on this material are compared with results found in other microwave bolometry experiments, and found to be in qualitative agreement.

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