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oai:www.ideals.illinois.edu:2142/23234 2023-07-10 col_2142_5131 col_2142_8859 com_2142_5130 com_2142_8858 com_2142_234

A low temperature calorimetric study of several high-T(c) superconductors text Ginsberg, Donald M. Reeves, Mark Edwin 2011-05-07T14:06:56Z 2011-05-07T14:06:56Z 10000-01-01 1989 Sintered powders of La$\sb{1.85}$Ba$\sb{0.15}$CuO$\sb4$, La$\sb{1.8}$Sr$\sb{0.2}$CuO$\sb4$, YBa$\sb2$Cu$\sb3$O$\sb{\rm7-x}$, and GdBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ were prepared by solid state reaction. The samples were carefully characterized for impurities by x-ray diffraction and Raman spectroscopy. The resistivity and magnetic susceptibility of each sample was measured to characterize its superconducting transition. The specific heat of the samples was measured with an adiabatic, computer-controller calorimeter. The specific heat discontinuity for GdBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ was determined, and antiferromagnetic ordering and superconductivity were observed to coexist in this sample. For all the samples, a temperature dependent phonon density of states was inferred from the specific heat measured above 10K. While the temperature range of the measurements extended from 2 to 180K, particular attention was paid to the specific heat below 10K. In this temperature range, the lattice and electronic contributions to the specific heat could be separated. In all the samples measured except for GdBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ an unexpected linear contribution to the specific heat was observed. By systematically eliminating the known impurities in a sample of YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ and still observing the linear contribution, we argue against attributing this contribution to a parasitic phase. The magnetic field dependence of the specific heat of YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ was determined for fields from 0 to 3T and in the temperature range 2 to 10K. The field dependence was compared to a calculation based on Ginzburg-Landau theory. The theory did not predict our experimental results. Made available in DSpace on 2011-05-07T14:06:56Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9010996.pdf: 5927079 bytes, checksum: 6e538d32e275157dfb17494c8a7881de (MD5) Previous issue date: 1989 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:03:05Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:30:03-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9010996 (UMI)AAI9010996 http://hdl.handle.net/2142/23234 eng Copyright 1989 Reeves, Mark Edwin Physics, Condensed Matter Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.