Calorimetric determination of the upper critical fields and anisotropy of NdFeAsO{sub 1-x}F{sub x} single crystals.
We present heat-capacity measurements of the upper critical fields of single-crystal NdFeAsO{sub 1?x}F{sub x}. In zero-magnetic field a clear step in the heat capacity is observed at T{sub c} {approx} 47 K. In fields applied perpendicular to the FeAs layers the step broadens significantly whereas for the in-plane orientation the field effects are small. This behavior is reminiscent of the CuO{sub 2}-high-T{sub c} superconductors and is a manifestation of pronounced fluctuation effects. Using an entropy conserving construction we determine the transition temperatures in applied fields and the upper critical-field slopes of {partial_derivative}H{sup c}c2/{partial_derivative}T = -0.72 T/K and {partial_derivative}H{sup ab}c2/{partial_derivative}T = -3.1 T/K. Zero-temperature coherence lengths of {zeta}{sub ab} {approx} 3.7 nm and {zeta}{sub c} {approx} 0.9 nm and a modest superconducting anisotropy of {lambda} {approx} 4 can be deduced in a single-band model.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); Natural Science Foundation of China; Ministry of Science and Technology of China; Chinese Academy of Sciences
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 947537
- Report Number(s):
- ANL/MSD/JA-62351; TRN: US200905%%8
- Journal Information:
- Phys. Rev. B, Vol. 78, Issue 2008; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Specific heat and phase diagrams of single crystal iron pnictide superconductors.
Upper critical fields and thermally-activated transport of Nd(0.7Fe0.3) FeAs single crystal