Microscopic measurement of penetration depth in YBa2Cu3O7-δ thin films by scanning Hall probe microscopy

We have used a low noise scanning Hall probe microscope to measure the penetration depth microscopically in a YBa2Cu3O7-δ thin film as a function of temperature. The instrument has high magnetic field (approx. 2.9x10-8 T Hz-1/2 at 77 K) and spatial resolution (approx. 0.85 μm). Magnetic field profiles of single vortices in the superconducting film have been successfully measured and the microscopic penetration depth of the superconductor has been extracted. We find surprisingly large variations in values of λ for different vortices within the scanning field. (author)