Thermally-activated and temperature-independent magnetic relaxation in aligned grains of NdFeAsO(F)

ORAL

Abstract

We have studied flux creep in a magnetically-aligned powder of NdFeAsOF and found it to be strikingly similar to the situation in cuprates. The magnetic relaxation rate S=-dlnM$_{irr}$/dlnt is linear in temperature at low temperatures. There is an extrapolated~finite creep rate of about S=-0.02 at T=0, indicative of a quantum tunneling of vortices under energy barriers. This quantum creep rate is field-independent. From the temperature-dependent creep data we have obtained activation energy as a function of persistent current density, U(J). Comparison with existing creep theories will be made.

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Authors

  • J.R. Thompson

    Dept. of Physics, University of Tennessee and Oak Ridge National Laboratory, Dept Physics, Univ. Tennessee, Knoxville, TN, USA, U. of Tennessee, Dept. of Physics, University of Tennessee, and Oak Ridge National Laboratory, University of Tennessee

  • Yuri L. Zuev

    Oak Ridge National Laboratory

  • D. K. Christen

    Oak Ridge National Laboratory

  • E. D. Specht

    Oak Ridge National Laboratory

  • R. Jin

    Oak Ridge National Laboratory, Materials Science \& Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  • Brian C. Sales

    Oak Ridge National Laboratory, Materials Science \& Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  • Michael A. McGuire

    Oak Ridge National Laboratory, Materials Science \& Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  • A. Sefat

    Oak Ridge National Laboratory, Materials Science \& Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  • D. G. Mandrus

    Oak Ridge National Laboratory, Oak Ridge National Laboratory, University of Tennessee, Materials Science \& Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA