07. Local measurement of the penetration depth in the pnictide superconductor Ba(Fe0.95Co0.05)2As2

We use magnetic force microscopy (MFM) to measure the local penetration depth λ in Ba ( Fe 0.95 Co 0.05 ) 2 As 2 single crystals and use scanning superconducting quantum interference device susceptometry to measure its temperature variation down to 0.4 K. We observe that superfluid density ρ s over the full temperature range is well described by a clean two-band fully gapped model. We demonstrate that MFM can measure the important and hard-to-determine absolute value of λ , as well as obtain its temperature dependence and spatial homogeneity. We find ρ s to be uniform on the submicron scale despite the highly disordered vortex pinning.