Abstract
We measure magnetotransport of F-doped SmFeAsO samples up to 28 T and we extract the upper critical fields, using different criteria. In order to circumvent the problem of criterion-dependent values, we suggest a thermodynamic estimation of the upper critical field slope based on the analysis of conductivity fluctuations in the critical regime. A high field slope as large as is thus extracted for the optimally doped sample. We find evidence of a two-dimensional lowest Landau level (LLL) scaling for applied fields larger than . Finally, we estimate the coherence length values and we observe that they progressively increase with decreasing . In all cases, the coherence length values along the axis are smaller than the interplanar distance, confirming the two-dimensional nature of superconductivity in this compound.
- Received 30 January 2009
DOI:https://doi.org/10.1103/PhysRevB.79.104515
©2009 American Physical Society