High-Field Pauli-Limiting Behavior and Strongly Enhanced Upper Critical Magnetic Fields near the Transition Temperature of an Arsenic-Deficient LaO0.9F0.1FeAs1-δ Superconductor

We report upper critical field B-c2(T) data for disordered (arsenic-deficient) LaO0.9F0.1FeAs1-delta in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of B-c2 approximate to-5.4 to -6.6 T/K near T-c approximate to 28.5 K, the T dependence of the in-plane B-c2(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with B-c2(0)approximate to 63-68 T. Our results are discussed in terms of disorder effects within conventional and unconventional superconducting pairings.