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      Permanent link:
      https://www.ias.ac.in/article/fulltext/pram/071/05/0901-0901

    • Keywords

       

      Neutron scattering; magnetic systems.

    • Abstract

       

      Non-exponential relaxation is a universal feature of systems as diverse as glasses, spin glasses, earthquakes, financial markets and the universe. Complex relaxation results from hierarchically constrained dynamics with the strength of the constraints being directly related to the form of the relaxation, which changes from a simple exponential to a stretched exponential and a power law by increasing the constraints in the system. A global and unified approach to non-exponentiality was first achieved by Weron and was further generalized by Brouers and Sotolongo-Costa, who applied the concept of non-extensive entropy introduced by Tsallis to the relaxation of disordered systems.

      These concepts are now confronted with experimental results on the classical metallic spin glasses CuMn, AuFe and the insulating system EuSrS. The revisited data have also be complemented by new results on several compositions of the classical CuMn spin glass and on systems, like CoGa and CuCo, the magnetic behaviour of which is believed to arise from magnetic clusters and should be characteristic for superparamagnetism.

    • Author Affiliations

       

      R M Pickup1 R Cywinski1 C Pappas2 P Fouquet3 B Farago3 P Falus

      1. School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
      2. Hahn-Meitner Institut, Glienicker Straße 100, 14109 Berlin, Germany
      3. Institut Laue-Langevin, 6, Rue Jules Horowitz, 38042 Grenoble, France
    • Dates

       
  • Pramana – Journal of Physics | News

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