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Evidence for Two Distinct Anisotropies in the Oxypnictide Superconductors SmFeAsO0.8F0.2 and NdFeAsO0.8F0.2

  • S. Weyeneth
  • R. Puzniak
  • N. D. Zhigadlo
  • S. Katrych
  • Z. Bukowski
  • J. Karpinski
  • H. Keller
Letter

Abstract

Single crystals of the oxypnictide superconductors SmFeAsO0.8F0.2 and NdFeAsO0.8F0.2 with T c in the range of 44 to 48 K were investigated by torque magnetometry. An analysis of the data in terms of a recently proposed model for the anisotropic magnetization in the superconducting state, treating the magnetic penetration depth anisotropy γ λ differently than the upper critical field anisotropy γ H , provides evidence that in the oxypnictide superconductors two distinct anisotropies are present. As a result γ λ differs significantly in magnitude and in temperature dependence from γ H , analogous to MgB2 but with a reversed sign of slope. This scenario strongly suggests a new multi-band mechanism in the novel class of oxypnictide high-temperature superconductors.

Keywords

Oxypnictides Anisotropy Multi-band superconductivity Single crystal Torque magnetometry Magnetic penetration depth Upper critical field 

PACS

74.70.Dd 74.25.Ha 74.20.De 74.25.Op 

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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • S. Weyeneth
    • 1
  • R. Puzniak
    • 2
  • N. D. Zhigadlo
    • 3
  • S. Katrych
    • 3
  • Z. Bukowski
    • 3
  • J. Karpinski
    • 3
  • H. Keller
    • 1
  1. 1.Physik-Institut der Universität ZürichZürichSwitzerland
  2. 2.Institute of PhysicsPolish Academy of SciencesWarsawPoland
  3. 3.Laboratory for Solid State PhysicsETH ZurichZurichSwitzerland

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