The magnetization distribution in the L21 phase of a type of ferromagnetic shape memory alloy, Ni2Mn(Al,Ga), was studied by means of electron holography and Lorentz microscopy. The alloy contained many antiphase boundaries, which were introduced by chemical ordering from the B2 state to the L21 state. In situ Lorentz microscopic observations had revealed that antiphase boundaries behaved as strong pinning sites for domain-wall motion. The width of a 180° wall, which was formed at the position of an antiphase boundary, was estimated to be about 10nm. This narrow domain wall was associated with a depression of ferromagnetism within antiphase boundaries.

Interaction between Magnetic Domain Walls and Antiphase Boundaries in Ni2Mn(Al,Ga) Studied by Electron Holography and Lorentz Microscopy. T.Yano, Y.Murakami, R.Kainuma, D.Shindo: Materials Transactions, 2007, 48[10], 2636-41