Abstract
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 . The anisotropy of the penetration depth is temperature independent and on the order of . Similarly specific-heat data lead to an anisotropy of the coherence length close to . Our results suggest the presence of rather large thermal fluctuations and the existence of a vortex liquid phase over a broad temperature range ( large at 2 T).
- Received 15 December 2008
DOI:https://doi.org/10.1103/PhysRevB.79.020508
©2009 American Physical Society