Small angle electron diffraction and Foucault mode Lorentz microscopy of superconducting vortex lattice

Small angle electron diffraction patterns from vortex lattices in Nb thin films were observed using a field emission transmission electron microscope. It was possible to obtain diffraction patterns in magnetic fields of up to 1000 G, from selected areas of (1–10) μm in diameter, and in (1–30) s. The degree of order of the vortex lattice was determined from the fine structure of the diffraction pattern. We also demonstrated Foucault mode Lorentz microscopy by using a diffraction technique. Vortices appeared by diffraction contrast in a focused micrograph, and therefore both vortices and material defects were simultaneously observed.