uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The paramagnetic Meissner effect
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The low field dynamics of some high temperature superconductors have been studied experimentally, using SQUID magnetometry.

The research has been focused on the so called Paramagnetic Meissner Effect (PME), a phenomenon seen in some high temperature superconducting cuprates. The signature of this effect is a positive magnetisation when the sample is cooled through its superoconducting transition temperature in sufficiently low magnetic fields. The PME has been explained in terms of spontaneously created magnetic moments, formed in zero magnetic field, a consequence of unconventional symmetry of the superconducting order parameter, which allows the creation of π-junctions. A detailed study of the system Bi2Sr2CaCu2O8 has revealed fundamental characteristics of systems exhibiting PME. It is found that the out-of-phase component of the ac susceptibility is suppressed for small external de fields, for ac field amplitudes in the linear response regime. Furthermore, the spontaneous flux noise also decreases for small superimposed de fields. A good agreement between the two quantities, according to the Fluctuation- Dissipation Theorem, has been found both in zero and small external de fields.

The dc magnetisation has been studied as a function of time. It has been shown that the relaxation of the zfc magnetisation displays zero external field magnetic ageing, revealing a collective behaviour of the spontaneous magnetic moments. The collective behaviour points out that intrinsically the ensemble of the spontaneous magnetic moments is disordered and frustrated. The collective behaviour has been discussed in terms of a novel equilibrium thermodynamic phase, the so called "chiral-glass" phase. Dynamic and static scaling analyses of the experimented data have been performed, giving indications, although not unambiguous evidence, of a "chiral-glass" phase at low temperatures.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2001. , 43 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 614
Keyword [en]
Materials science, high-temperature superconductivity, Bi-based compounds, paramagnetic Meissner effect, ageing, disordered magnets, chiral-glass
Keyword [sv]
Materialvetenskap
National Category
Materials Engineering
Research subject
Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-1263ISBN: 91-554-4974-3 (print)OAI: oai:DiVA.org:uu-1263DiVA: diva2:160825
Public defence
2001-04-09, Polhemsalen at the Ångström Laboratory, Uppsala University, Uppsala, 10:15 (English)
Available from: 2001-03-19 Created: 2001-03-19 Last updated: 2009-08-26Bibliographically approved

Open Access in DiVA

No full text
Buy this publication >>

By organisation
Department of Materials Science
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 713 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf