A new method for investigating dynamic processes in transmission electron microscopy is proposed and demonstrated for Lorentz microscopy measurement of vortex motion in a Nb thin film. A selected portion of the electron beam current, modulated by the dynamics of the specimen, is led through the probe aperture at the image plane and measured as sequential counts of electrons or as a correlation function. The free energy barrier of the vortex hopping and the local creeping velocity are determined. In addition, the feasibility of observing the elastic flow of vortices is shown.

• Received 2 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.1711