Skip navigation
  • Home
  • Browse
    • Communities
      & Collections
    • Browse Items by:
    • Publication Date
    • Author
    • Title
    • Subject
    • Department
  • Sign on to:
    • My MacSphere
    • Receive email
      updates
    • Edit Profile


McMaster University Home Page
  1. MacSphere
  2. Open Access Dissertations and Theses Community
  3. Open Access Dissertations and Theses
Please use this identifier to cite or link to this item: http://hdl.handle.net/11375/12593
Title: NMR STUDY OF THE POTASSIUM IRON SELENIDE HIGH-TEMPERATURE SUPERCONDUCTOR
Authors: Torchetti, David
Advisor: Imai, Takashi
Department: Physics and Astronomy
Keywords: Superconductvitiy;nuclear magnetic resonance;potassium iron selenide;high-temperature iron-based superconductor;Condensed Matter Physics;Condensed Matter Physics
Publication Date: Oct-2012
Abstract: <p>In this thesis we present a <sup>77</sup>Se NMR study of the iron selenide based high-temperature superconductor K<sub>x</sub>Fe<sub>2−y</sub>Se<sub>2</sub> (T<sub>c</sub> = 33 K). We observe NMR lineshapes as narrow as ∼ 4.5 kHz with an applied field along the crystal c-axis, and find no evidence for the co-existence of magnetic order with superconductivity. With an applied field along the ab plane, however, the lineshape splits into two peaks of equal intensities at all temperatures, suggesting that the tetragonal fourfold symmetry of the average structure may be locally lowered by vacancy superstructure. Knight shift data indicate that spin susceptibility decreases progressively with temperature, similar to other iron arsenide high-T<sub>c</sub> systems. In the nuclear spin-lattice relaxation rate 1/T<sub>1</sub> we observe no Hebel-Slichter coherence peak, nor any enhancement in low frequency antiferromagnetic spin fluctuations in 1/T<sub>1</sub>T. We also report on the effects of sulphur (S) substitution on the selenium sites in this system by conducting <sup>77</sup>Se NMR measurements on K<sub>x</sub>Fe<sub>2−y</sub>Se<sub>2−z</sub>S<sub>z</sub> (z = 0.8, 1.6). We find that both spin susceptibility and low frequency spin fluctuations are suppressed with increasing S content along with T<sub>c</sub>.</p>
URI: http://hdl.handle.net/11375/12593
Identifier: opendissertations/7466
8521
3348826
Appears in Collections:Open Access Dissertations and Theses

Files in This Item:
File SizeFormat 
fulltext.pdf
Open Access
2.23 MBAdobe PDFView/Open
Show full item record Statistics


Items in MacSphere are protected by copyright, with all rights reserved, unless otherwise indicated.

Sherman Centre for Digital Scholarship     McMaster University Libraries
©2022 McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8 | 905-525-9140 | Contact Us | Terms of Use & Privacy Policy | Feedback

Report Accessibility Issue