High Voltage Scanning Electron Microscopy for Observing Magnetic Domains

Abstract

Magnetic domain contrast in a SEM image of cubic ferromagnetic materials enhances with increasing accelerating voltage. It was shown that a high voltage SEM was effective for observing the domain structure in a very small saturation magnetization material. It is however known that the high voltage SEM observation is not so desirable because of increased electron diffusion. Thus further investigations are still needed. By utilizing a 200 kV SEM, JSEM-200, with the backscattered mode, we have found that the increased accelerating voltage results not only in the enhancement of magnetic contrast but also in a great reduction of topographical contrast caused by the surface projections as well as that of electron channeling contrast (see Figs. 1 and 2). Moreover we successfully observed the domain structures of a Goss-oriented 3% Si-Fe sheet whose surface was covered by an insulator (like glass) film of 4.5 μm in thickness (see Fig. 3). The domains were clearly observed at 200 kV but unobservable at 100 kV. These features are particularly useful for studying the domain structures in the practical materials.