Broadband microwave spectroscopy of YBa[sub 2]Cu[sub 3]O[sub 6+y]
department or school: Science, Faculty of
department or school: Physics and Astronomy, Department of
data provider: DSpace
degree campus: UBCV
creator: Turner, Patrick James
issued: 2009-12-02T00:00:00
issued: 2004
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: A novel low temperature bolometric method has been devised and implemented for high-precision measurements of the microwave surface resistance of small singlecrystal platelet samples having very low absorption, as a continuous function of frequency from 0.5 GHz to 21 GHz. The key to the success of this non-resonant method is the in-situ use of a normal metal reference sample that calibrates the absolute rf field strength. The sample temperature can be controlled independently of the 1.2 K liquid helium bath, allowing for measurements of the temperature evolution of the absorption. Using this method, the minimum detectable power at 1.3 K is 1.5 pW, corresponding to a surface resistance sensitivity of approximately 1 μΩ for a typical 1 mm x 1 mm platelet sample. Using this apparatus, the zero-field electron spin resonance absorption spectrum of a dilute array of Gd ions substituted for Y in YBa₂Cu₃O[sub 6+y] was used as a unique means of accessing the absolute value of the low temperature magnetic penetration depth λ(T → 0) in the Meissner state. The result is a new set of precise values of λ for screening currents along the three principal crystallographic orientations in samples of Gd[sub x]Y[sub 1-x]Ba₂Cu₃O[sub 6+y] for three different oxygen-ordered phases having T[sub c] values of 89 K, 75 K and 56 K. The in-plane values are found to depart substantially from the widely-reported relation T[sub c] ∝ 1/ λ² inferred mainly from muon spin relaxation measurements on polycrystalline materials. The broadband microwave spectrometer has allowed measurements in unprecedented detail of the in-plane microwave absorption in high-purity YBa₂Cu₃O[sub 6+y] single crystals. This has permitted, for the first time, the observation of the cuspshaped conductivity spectra characteristic of weak-limit scattering from impurities in a d-wave superconductor. A comparison of the detailed measurements for samples of ortho-II ordered YBa₂Cu₃O₆.₅₂ (T[sub c] =56 K) and fully-doped YBa₂Cu₃O₆.₉₉…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/16075
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note: Broadband Microwave Spectroscopy of Y B a 2 C u 3 0 by Patrick James Turner B.Sc , McMaster University, 1997 M . S c , The University of British Columbia, 1999 A THESIS S U B M I T T E D IN P A R T I A L F U L F I L M E N T OF T H E R E Q U I R E M E N T S F O R T H E D E G R E E OF D O C T O R OF P H I L O S O P H Y in The Faculty of Graduate Studies (Department of Physics and Astronomy) We accept this thesis as conforming to the required standard g -3 T H E U N I V E R S I T Y OF BRITISH C O L U M B I A Apri l 6, 2004 © Patrick James Turner, 2004 Abstract i i Abstract A novel low temperature bolometric method has been devised and implemented for high-precision measurements of the microwave surface resistance of small single-crystal platelet samples having very low absorption, as a continuous function of fre-quency from 0.5 GHz to 21 GHz. The key to the success of this non-resonant method is the in-situ use of a normal metal reference sample that calibrates the absolute rf field strength. The sample temperature can be controlled independently of the 1.2 K liquid helium bath, allowing for measurements of the temperature evolution of the absorption. Using this method, the minimum detectable power at 1.3 K is 1.5 pW, corresponding to a surface resistance sensitivity of approximately 1 pQ for a typical 1 m m x l mm platelet sample. Using this apparatus, the zero-field electron spin resonance absorption spectrum of a dilute array of Gd ions substituted for Y in YBa 2 Cu306+ y was used as a unique means of accessing the absolute value of the low temperature magnetic penetration depth X(T —> 0) in the Meissner state. The result is a new set of precise values of A for screening currents along the three principal crystallographic orientations in samples of Gd x Yi_ x Ba2Cu306+ y for three different oxygen-ordered phases having Tc values of 89 K, 75 K and 56 K . The in-plane values are found to depart substantially from the widely-reported relation Tc oc 1/A2 inferred mainly…
has type: Thesis/Dissertation
date issued: 2004-05
is shown at: 10.14288/1.0085727
language: eng
degree discipline: Physics
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/16075