Domain Pattern Movements in Silicon-Iron Observed by Electron Mirror Microscopy

Abstract

Recent results of the application of electron mirror microscopy for magnetic investigations are reported. It is shown that electron mirror microscopy reveals magnetic domain patterns not only in magnetic materials with a uniaxial direction of easy magnetization but also in materials with several directions of easy magnetization exhibiting basically flux closure domain configurations. On silicon-iron specimens three types of domain manifestation were observed. In two types normal components of the magnetic fields above the entire extension of the domains, weak as they may be, permit the observation. In cases where no such magnetic field components exist, domain walls proper can be observed if magnetic fields are applied. This possibility probably stems from an unsymmetry of the magnetic field above domain walls when a magnetic field is applied. Movements in the domain patterns and domain wall motions can be observed instantaneously because electron mirror microscopy is unhampered by time delays inherent in the Bitter technique. This electronic observation method is also applicable at temperatures at which conventional methods fail. Motion pictures photographed directly from the viewing screen of the electron mirror microscope portray quite adequately the domain patterns set in motion by applied magnetic fields.