Log-T upturn in resistivity of lightly-doped oxypnictide superconductor in an intense magnetic field

ORAL

Abstract

We report the resistivity of a series of fluorine-doped SmFeAsO$_{1-x}$F$_x$ polycrystalline superconductors in magnetic fields up to 60 T. For underdoped samples ($x < 0.15 $), the low-temperature resistive state is characterized by pronounced magneto-resistance including an upturn in the resistivity at low temperatures. The ``insulating behavior'' is characterized by a log-T divergence observed over a decade in temperature. In contrast, samples with doping $x > 0.15$ display metallic behavior with little magnetoresistance, where intense magnetic fields serve to broaden the superconducting transition rather than significantly suppress T$_c$. The doping regime for the log-T behavior coincides with the spin density wave (SDW) in the phase diagram for SmFeAsO$_{1-x}$F$_x$.

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Authors

  • Z. Stegen

    • National High Magnetic Field Laboratory, Florida State University

  • S.C. Riggs

    • National High Magnetic Field Laboratory, Florida State University

  • J.B. Kemper

    • National High Magnetic Field Laboratory, Florida State University

  • Y. Jo

    • National High Magnetic Field Laboratory, Florida State University

  • L. Balicas

    • National High Magnetic Field Laboratory, Florida State University

  • G.S. Boebinger

    • National High Magnetic Field Laboratory, Florida State University

  • F.F. Balakirev

    • National High Magnetic Field Laboratory, Los Alamos National Laboratory

  • A. Migliori

    • National High Magnetic Field Laboratory, Los Alamos National Laboratory

  • H. Chen

    • Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China

  • R.H. Liu

    • Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China

  • X.H. Chen

    • Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China