University of Illinois Urbana-Champaign

Experimental observations on some reduced-oxygen Chevrel-phase compounds

Wright, William Harrison

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https://hdl.handle.net/2142/25449

Description

Title
Experimental observations on some reduced-oxygen Chevrel-phase compounds
Author(s)
Wright, William Harrison
Issue Date
1987
Doctoral Committee Chair(s)
Ginsberg, D.M.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • reduced-oxygen chevrel-phase compounds
  • temperature dependence
  • magnetic susceptibility
  • Pauli susceptibility
Language
en
Abstract
We have developed a refined procedure for removing oxygen from the Chevrel phase compounds SnMo6Sg, PbMo6Sg, and Cu1.gMo6Sg. Measurements of the temperature dependence of the magnetic susceptibility have been made on these gettered Chevrel compounds, and comparisons have been made between the Pauli susceptibility of gettered and ungettered compounds. The Pauli susceptibility is proportional to the electronic density of states, and the changes in the density of states are used to explain the increase in the superconducting transition temperature of gettered SnMo6Sg and PbMo6S8. Evidence for a structural phase transition is seen in the temperature dependence of the magnetic susceptibility of SnMo6Sg. The temperature dependence of the upper critical field was measured for gettered SnMo6S8 and PbMo6Sg. The initial slope of the critical field is shallower for the gettered compounds than for ungettered compounds. The effects of doping oxygen into the small-cation Chevrel compound Cu1.8Mo6s8 have been studied, and these effects have been found to be different than those observed in the large-cation compounds SnMo6Sg and PbMo6Sg. Oxygen increases the superconducting transition temperature of Cu1.8Mo6S8-xOx, but decreases the electronic density of states as seen in the magnetic susceptibility. The temperature dependence of the magnetic susceptibility of both Cu1.gMo6S8 and Cu3.2Mo6S8 has been investigated, and we see evidence of the phase transitions in these compounds. We see an unusual time dependence of the magnetic susceptibility for Cu3.2Mo6S8. The derivative of the upper critical field of Cu1.8Mo6S8-xOx with respect to temperature does not seem to be affected by the oxygen concentration. We have investigated the dependence of the superconducting transition temperature on the tungsten concentration in WxSnt-xMo6S8 and have found an unusual peak in the curve. We explain this in terms of tungsten transferring more charge to the Mo6S8 clusters than the tin atoms it replaces.
Type of Resource
text
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http://hdl.handle.net/2142/25449
Copyright and License Information
1987 William Harrison Wright III

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Graduate Theses and Dissertations at Illinois