Evidence for Two Distinct Anisotropies in the Oxypnictide Superconductors SmFeAsO0.8F0.2 and NdFeAsO0.8F0.2 |
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Authors: | S Weyeneth R Puzniak N D Zhigadlo S Katrych Z Bukowski J Karpinski H Keller |
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Affiliation: | 1. Physik-Institut der Universit?t Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland 2. Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668, Warsaw, Poland 3. Laboratory for Solid State Physics, ETH Zurich, 8093, Zurich, Switzerland
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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.
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Keywords: | Oxypnictides Anisotropy Multi-band superconductivity Single crystal Torque magnetometry Magnetic penetration depth Upper critical field |
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