Cryogenic scanning Hall-probe microscope with centimeter scan range and submicron resolution

We have constructed a scanning Hall-probe microscope that combines a 1x4 cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. The instrument is uniquely suited for efficient magnetic imaging of mesoscopic devices, media, and materials, operating from 4 K to room temperature with fast turn-around time. Its potential for studying dissipation in coated conductors-high-T-c superconducting tapes-is demonstrated via model systems. We image an entire sample of YBa2Cu3O7-delta, then zoom in to individual fluxons. Flux penetration into a single artificial grain boundary is imaged with 4x10(-3) G/root Hz field resolution and 25 mu s time resolution by averaging over cycles of ac driving current. Using the resulting magnetic movie, we map out ac power losses.