Single-vortex pinning and penetration depth in superconducting NdFeAsO1-xFx
We use a magnetic force microscope (MFM) to investigate single-vortex pinning and penetration depth in NdFeAsO1−xFx, one of the highest-Tc iron-based superconductors. In fields up to 20 G, we observe a disordered vortex arrangement, implying that the pinning forces are stronger than the vortex-vortex interactions. We measure the typical force to depin a single vortex, Fdepin≃4.5 pN, corresponding to a critical current up to Jc≃7×105 A/cm2. Furthermore, our MFM measurements allow the first local and absolute determination of the superconducting in-plane penetration depth in NdFeAsO1−xFx,λab=320±60 nm, which is larger than previous bulk measurements.
This article is published as Zhang, Jessie T., Jeehoon Kim, Magdalena Huefner, Cun Ye, Stella Kim, Paul C. Canfield, Ruslan Prozorov, Ophir M. Auslaender, and Jennifer E. Hoffman. "Single-vortex pinning and penetration depth in superconducting NdFeAsO 1− x F x." Physical Review B 92, no. 13 (2015): 134509. DOI: 10.1103/PhysRevB.92.134509. Posted with permission.