Direct Observation of Interlayer Josephson Vortices in Heavily Pb-Doped Bi_2Sr_2CaCu_2O_y by Scanning Superconducting Quantum Interference Device Microscopy

摘要

Josephson vortices trapped in cross-sectional edge surfaces of Pb_(0.6)Bi_(1.4)Sr_2CaCu_2O_y has been directly observed by using a scanning superconducting quantum interference device (SQUID) microscope. The magnetic field distribution B_z around each vortex is substantially anisotropic, compared with the usual vortex in the ab-plane, and is extended over 100 μm toward the in-plane direction. By fitting a theoretical B_z function to experimental ones, c-axis penetration depth λ_c was estimated to be 11.2 ± 0.7 μm, which is in good agreement with the literature value, 12.6 μm, obtained from the Josephson plasma edge frequency.