Y. Murakami, T. Yano, D. Shindo, R. Kainuma, Tohoku University, Sendai, Japan
A Ni2Mn(Al,Ga) alloy contains many anti-phase boundaries (APBs) due to the B2→L21 ordering in the parent phase. Electron holography and Lorentz microscopy studies have revealed that the magnetic domain walls are placed at the positions of APBs in the L21-ordered parent phase: the result indicates that the domain wall energy is minimized at the position of APBs. In fact, the magnetization process in the parent phase proceeds in the following sequence: (1) When a magnetic field is applied to a thin-foiled specimen, the magnetization distribution first changes in the portions that are distant from APBs. (2) In a larger magnetic field, the magnetic domain walls at the positions of APBs are released. However, the released walls are immediately trapped by nearby APBs. Thus, the domain wall motion occurs intermittently, rather than continuously.
