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Title: Approaching isotropy in the vortex system of SmFeAs(O,F) at extreme magnetic fields

The role of anisotropy in the iron-pnictides is one of the key questions in understanding their high-temperature superconductivity. The inherent layeredness of these systems, consisting of FeAs layers separated by various layers, gives rise to an upper critical field anisotropy γ(Tc) ~ 3 in the “122” system (i.e. (Ba,K)Fe2As2) and up to 6-8 in the “1111” system (i.e. SmFeAs(O,F)). In the “122” compounds, this anisotropy is known to decrease upon cooling, converging to almost isotropic superconductivity at lowest temperatures[1]. This can be understood through a particular temperature dependence of the inter- and intra-band scattering. The “1111” class is naturally more anisotropic due to the thicker SmO blocking layer, and the much higher upper critical fields (Hc2, HIIab(0)>>100T) cannot be reached at low temperature. Despite this challenging field requirement, the aim of this project is to discern whether this emergent isotropy in the “122” materials is a property of all FeAs classes. Focused Ion Beam (FIB) micromachined samples have in the past proven to be particularly well suited for pulsed magnetic fields[2]. Employing the micrometer precision of the FIB, we fabricated three individual samples on a 2x2 mm chip and thus maximized the acquired transport data per pulse.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2]
  1. ETH Zurich (Switzerland)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
OSTI Identifier:
1114402
Report Number(s):
LA-UR--14-20072
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE; NSF
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE High Magnetic Field Science