How does B-H hysteresis curve be understood in terms of domain growth and domain rotation?
There are two possible ways to align a random domain structure by applying an electric field. One is to rotate a domain in the direction of field and other is to allow the growth of the favourably oriented domains at the expense of less favourably oriented ones. If domain structure is compared with grain structure of a polycrystalline material, boundaries separating the domains known as called domains walls are analogue of grain boundaries. Domain boundary energy is about 0.0002 J/m2. Domain walls however are some two orders of magnitude thicker than grain boundaries, since there is a gradual transition from one domain orientation to next across the wall. Additionally domain boundaries can exist within the grain. Analogous to grain growth, domain walls can move such that more favourably oriented domains grow at expense of others. In earlier stages of magnetization below the saturation region of hysteresis curve, domain growth is dominant. Growth is more or less complete as the saturation region is approached.