2011 年 54 巻 4 号 p. 256-263
Magnetic structures in advanced functional materials were studied by electron holography and Lorentz microscopy, both of which are the methods of magnetic imaging based on transmission electron microscopy. The microscopy observations revealed that anti-phase boundaries (APBs: planar lattice imperfections) formed in a ferromagnetic shape memory alloy provided significant pinning sites for the magnetic domain walls. The width of magnetic domain walls trapped by APBs was only 10 nm, which was considerably smaller than the width of conventional 180° walls formed in cubic systems: this narrow wall width was reasonably explained by the depression of ferromagnetism within APBs. We also report on the original method to determine magnetic parameters, related to the exchange stiffness and the magnetocrystalline anisotropy, by using only electron microscopy observations.