Magnetic domain structures of Nd2Fe14B based permanent magnets were studied by using electron holography and Lorentz microscopy. In a sintered Nd2Fe14B permanent magnet, a domain wall width of a 180° magnetic domain was evaluated to be 5.1 nm by Lorentz microscopy, while the magnetization distribution in the 90° magnetic domain was clarified by electron holography. In overquenched Nd2Fe14B permanent magnets, the sharp difference in the magnetization distribution due to the heat treatment was clarified by electron holography. The different magnetic properties of the magnets was directly attributed to the difference of the magnetization distribution.
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