Disentangling nanoscale electric and magnetic fields by time-reversal operation in differential phase-contrast STEM

Abstract

Differential phase-contrast (DPC) scanning transmission electron microscopy (STEM) has recently attracted significant interest for allowing mapping of electrostatic and magnetic fields at a high spatial resolution. Nevertheless, due to its simultaneous sensitivity to both electrostatic and magnetic fields, the interpretation of DPC measurements on magnetic specimens is not straightforward. In this work, we demonstrate that the two contributions to the Lorentz force can be separated by means of the time-reversal operation of the electron beam. In practice, such a condition is easily achieved by repeating the DPC-STEM measurement after flipping the specimen by 180°. The separation of the two contributions allows discriminating the effects of the electrostatic potential, like, e.g., the thickness variation in a specimen with a uniform composition, from the actual magnetic signal. This methodology is particularly relevant for the study of the magnetic nanostructure by DPC-STEM or, more generally, by 4D-STEM.