Upper and lower critical magnetic fields of superconducting NdFeAsO1−xFx single crystals studied by Hall-probe magnetization and specific heat

Z. Pribulova (1) , Thierry Klein (2) , J. Kacmarcik (1, 3) , C. Marcenat (3) , M. Konczykowski (4) , S. L. Bud'Ko (5) , M. Tillman (5) , P. C. Canfield (5)

1 CLTP IEP - Centre of Low Temperature Physics
2 NEEL - MagSup - Magnétisme et Supraconductivité
3 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
4 LSI - Laboratoire des Solides Irradiés - Irradiated Solids Laboratory
5 Ames Laboratory [Ames, USA]

The upper and lower critical fields have been deduced from specific heat and Hall-probe magnetization measurements in nonoptimally doped Nd O,F FeAs single crystals Tc 32-35 K . The anisotropy of the penetration depth is temperature independent and on the order of 4.0 1.5. Similarly specific-heat data lead to an anisotropy of the coherence length 5.5 1.5 close to Tc. Our results suggest the presence of rather large thermal fluctuations and the existence of a vortex liquid phase over a broad temperature range 5 K large at 2 T .

Mots clés: supraconductivité

Domaines: Supraconductivité [cond-mat.supr-con]

Z. Pribulova, Thierry Klein, J. Kacmarcik, C. Marcenat, M. Konczykowski, et al.. Upper and lower critical magnetic fields of superconducting NdFeAsO1−xFx single crystals studied by Hall-probe magnetization and specific heat. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009, 79, pp.020508(R). ⟨10.1103/PhysRevB.79.020508⟩. ⟨hal-00957171⟩