Electron holography for observing magnetic bubbles and stripe-shaped domains in magnetic fields.

An electron holography optical system was developed for relatively high magnetic fields up to 500 mT. The objective lens worked as a magnetic field generator for the specimen and the first intermediate lens worked for imaging as one of the pair lens composed of the objective lens. Specimen images were first formed on the object plane of the second intermediate lens. Electron biprism for conventional holography was installed under the second intermediate lens. Reconstruction of phase distributions was performed by the Fourier transform method and the vector maps were used to clarify small phase modulations. By using the developed system, magnetic characteristics of hexaferrite magnets (BaFeScMgO), such as magnetic bubbles and stripe-shaped magnetic domains, were observed at smaller than 200 mT. Their magnetization structures and their interactions are demonstrated with the experimental results.