• K Chandra

      Articles written in Pramana – Journal of Physics

    • On the behaviour of Er3+ ion in tetragonal crystalline field

      Vinod Kumar Narsingh Dass K Chandra

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      Crystal field parameters for ErGaG and Er3+ YAlG and used to compute the temperature dependence of Schottky specific heat, paramagnetic susceptibility, magnetic anisotropy,μeff and quadrupole splitting in the range 10–400 K. The hyperfine interaction parametersA andB for166Er and167Er in both the systems are also obtained and in turn used to estimate the nuclear specific heat contribution. The studied parameters compare well with the available experimental results.

    • Josephson voltage standard at National Physical Laboratory, New Delhi

      A K Gupta N S Natarajan V S Tomar N D Kataria V K Batra A V Narlikar K Chandra

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      A C Josephson effect is now used by several countries as the reference standard for the unit of d.c. voltage. This paper describes the work done at the National Physical Laboratory (NPL), New Delhi in the realization of the unit of volt based on the a.c Josephson effect. A voltage standard at 1 mV level using a Nb-Nb point contact junction has been established and the as-maintained volt based on a bank of standard cells has been intercompared against it using a 1:1000 voltage divider. The experimental set-up used in this comparison and the results of recent measurements are described. The overall uncertainty in assigning the value of emf to a standard cell is about 1 ppm. The as-maintained volt has been found to agree with the Josephson voltage within overall uncertainty.

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