Magnetic Domain Structures of Nd-Fe-B based Permanent Magnets Studied by Electron Holography and Lorentz Microscopy

Abstract

Magnetic domain structures of Nd 2 Fe 14 B based permanent magnets were studied by using electron holography and Lorentz microscopy. In a sintered Nd 2 Fe 14 B 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 Nd 2 Fe 14 B 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.