Visualizing flux distribution of superconductors in external magnetic fields with magnetic force microscopy

摘要

We visualized the flux distribution of a Bi_2Sr_2CaCu_2O_(8+δ) single crystal in transversal geometry by using low temperature magnetic force microscopy in the dynamic mode. With increasing external magnetic field, the magnetic flux density exhibited a distribution, which generally followed the Bean model. When the propagating flux front passed through the imaging area, we could observe a shift of the magnetic force microscopy signal toward an unexpected direction. The origin of this shift was studied by considering very long-range magnetic force due to the specific flux and current distribution near the propagating flux front.