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      Permanent link:
      https://www.ias.ac.in/article/fulltext/boms/002/03/0207-0216

    • Keywords

       

      Positron annihilation; lifetime; angular correlation; Doppler broadening; mixed valence; rare-earths; phase transition

    • Abstract

       

      Positron lifetime has been measured in SmS under external pressures from 0 to ∼ 16 kbar, and in (Sm0·8Gd0·2)S at temperatures from 10 K to 300 K. An abrupt drop in the lifetime was observed at the valence transition at a pressure of 6·5 kbar in SmS and at a temperature of ∼ 120 K in (Sm0·8Gd0·2)S. Measurement of the Doppler broadening of the annihilation photons was made in (Sm0·8 Gd0·2)S as a function of temperature. The line shape parameter of the Doppler broadened spectrum also showed an abrupt change at the transition. Angular correlation of annihilation photons was measured in the semiconducting phase of SmS and in the metallic phase of (Sm0·8Tb0·2)S. The correlation profile in the mixed valence (metallic) phase was broader than that in the semi-conducting phase. These results have been explained on the basis of the electronic structure of the semiconducting and the metallic phases of these materials.

    • Author Affiliations

       

      K P Gopinathan1 C S Sundar1 B Viswanathan1 A Bharathi1

      1. Reactor Research Centre, Kalpakkam - 603 102, India

    • Dates

       
      Published
      August 1980
      Manuscript received
      16 April 1980

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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