Abstract:The microstructure and coupling between structural and magnetic domains of ferromagnetic shape memory alloy Ni₅₅Mn_20.6Ga_24.4 were investigated by scanning electron acoustic microscopy (SEAM). Stripe ferroelastic domains (martensite variants) exist in every grain, and exhibit the configurations of the typical self-accommodation arrangement. Magnetic domain structure of Ni₅₅Mn_20.6Ga_24.4 was observed by the Bitter method and magnetic force microscopy (MFM). Due to the unique subsurface imaging capability of SEAM, combined with the Bitter method, the ferroelastic domain structure can be compared with in situ ferromagnetic domain structure. It is found that the martensitic variant boundaries coincide well with the ferromagnetic domain walls, which is beneficial for the understanding of the correlation between two kinds of ferroic domains.

Key words: ferroic domain; ferromagnetic shape memory alloy; scanning electron acoustic microscopy