Magnetic domain memory in multiferroic Ni 2 MnGa

Lorentz microscopy is employed to study the evolution of magnetic domain structures across ferromagnetic and ferroelastic martensitic transformations in near stoichiometric Ni 2 MnGa. In situ transmission electron microscopy studies have revealed a new phenomenon of magnetic domain memory of the austenite across both ferroic transformations. The reversible magnetic domain structure is attributed to pinning of the magnetic domain walls by antiphase boundaries in the Heusler phase. Two types of martensite domain structures, herringbone and stripe domain, have been observed. The type of domain arrangement is found to be dependent on the relative orientation of the easy axis of magnetization with respect to the thin foil normal.