Magnetic Domains and Twin Microstructure of Single Crystal Ni–Mn–Ga Exhibiting Magnetic Shape Memory Effect

Magnetic domains structure of a Ni-Mn-Ga single crystal was analyzed using a magneto-optical indicator film (MOIF), magnetic force microscopy (MFM), and scanning electron microscopy (SEM) (Lorenz contrast). Thanks to magnetically induced reorientation, the different configurations of magnetic domains can be obtained in the same place of the crystal. MOIF gives the overall domain configuration, while MFM shows the details of the structure revealing the domain branching. The magnetic domain structure in the vicinity of the mobile single twin boundary of Type II was observed by SEM and related to the complex twin structure of the martensite obtained from the calculation.