Lorentz microscopic observations of electrical steel sheets under an alternating current magnetic field

By utilizing an alternating current (AC) magnetic system recently installed on our transmission electron microscope (TEM), in-situ Lorentz microscope observations of electrical steel sheets were carried out under an AC magnetic field. The domain walls moved smoothly under a low frequency AC magnetic field. By using diffraction contrast, interactions between precipitates and the motion of the magnetic domain walls were visualized and clarified. Eventually, the magnetic domain walls were found to be pinned at strain fields around precipitates. Observations under higher frequency AC magnetic fields were also carried out. It was demonstrated that in-situ Lorentz microscopic observations under an AC magnetic field are very useful for the investigation of interactions between the microstructure and the motion of magnetic domain walls in electrical steel sheets.