Magnetic domain evolution with applied field in a Ni–Mn–Ga magnetic shape memory alloy

The evolution of a magnetic domain pattern with an applied field in two perpendicular directions was studied in a Ni–Mn–Ga magnetic shape memory alloy by means of optical and scanning electron microscopy (SEM). The optical contrast of magnetic domains arises from surface undulation. This surface relief is coherent at the (1 0 1) twin boundary. However, the surface relief causes the trace of the (0 1 1) twin boundary to follow a zigzag pattern. These optical observations were confirmed by SEM Type II magnetic contrast.