Observation of single vortices condensed into a vortex-glass phase by magnetic force microscopy

A low temperature magnetic force microscope has been applied to spatially resolve single vortices in an epitaxially grown YBa2Cu3 O7- thin film at 77 K. A disordered vortex arrangement is observed, and the vortices are strongly pinned. The observed phase is expected to be truly superconducting due to strong pinning. © 1995 The American Physical Society.