Field-induced nematic-like magnetic transition in an iron pnictide superconductor, Ca$_{10}$(Pt$_{3}$As$_{8}$)((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$

ORAL

Abstract

We report a high magnetic field study up to 55~T of the nearly optimally doped iron-pnictide superconductor Ca$_{10}$(Pt$_{3}$As$_{8}$)((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$ with a $T_{c} \approx$ 10 K using magnetic torque, tunnel diode oscillator technique and transport measurements. We determine the superconducting phase diagram, revealing an anisotropy of the irreversibility field up to a factor of 10 near $T_{c}$ and signatures of multiband superconductivity. Unexpectedly, we find a spin-flop like anomaly in magnetic torque at 22~T, when the magnetic field is applied perpendicular to the {\it ab} planes, which becomes significantly more pronounced as the temperature is lowered 0.33~K. As our superconducting sample lies well outside the antiferromagnetic region of the phase diagram, the observed field-induced transition in torque indicates a spin-flop transition \textit{not of long-range ordered moments}, but of nematic antiferromagnetic fluctuations. This work was supported by the EPSRC (EP/I004475/1) and EuroMagNET II.

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Authors

  • Matthew Watson

    • Oxford University, Clarendon Laboratory, UK
    • Clarendon Laboratory, University of Oxford, UK

  • Amalia Coldea

    • Oxford University, Clarendon Laboratory, UK
    • Clarendon Laboratory, University of Oxford, UK

  • Sam Blake

    • Clarendon Laboratory, University of Oxford, UK

  • Alix McCollam

    • High Field Magnet Laboratory, Radboud University, Nijmegen, The Netherlands

  • David Vignolles

    • Laboratoire National des Champs Magn\'{e}tiques Intenses, Toulouse, France

  • Loic Drigo

    • Laboratoire National des Champs Magn\'{e}tiques Intenses, Toulouse, France

  • Igor Mazin

    • Naval Research Laboratory, Washington, D.C., USA

  • Daniel Guterding

    • Institut f\"{u}r Theoretische Physik, Goethe-Universit\"{a}t Frankfurt, Germany

  • Harald Jeschke

    • Institut f\"{u}r Theoretische Physik, Goethe-Universit\"{a}t Frankfurt, Germany

  • Roser Valenti

    • Institut f\"{u}r Theoretische Physik, Goethe-Universit\"{a}t Frankfurt, Germany

  • Ni Ni

    • Department of Physics and Astronomy, University of California, Los Angeles

  • Robert Cava

    • Department of Chemistry, Princeton University, Princeton