Seeing with Phase: Interferometric Electron Microscopy for Magnetic Materials and Biological Specimens

Advances in imaging solid state materials at the nanoscale can lead to advances in imaging biological materials, and vice versa. For example, methods used to study biological materials in cryoEM are quite similar to methods developed for the study of magnetic materials. In both materials, features of interest are often only stable at low temperatures, and both are also essentially transparent to electrons. Materials composed of light elements such as biological specimens do not efficiently scatter electrons, and predominantly only impart subtle phase shifts to directly transmitted electrons. Likewise, nanoscale magnetic field textures inside samples do not scatter electrons, but introduce phase gradients onto the electrons. Thus, researchers in both cryoEM and nanomagnetic microscopy communities apply similar methods to provide phase contrast: defocus the instrument to a degree that subtle phase variations interfere to form observable intensity contrast. Perhaps new methods designed to image electric and magnetic fields more efficiently at higher resolutions can be applied to biological specimens.