It is shown that the domain structure, the properties of the special domain walls, and the shapes of the hysteresis loops can be explained by variations of K1 and Is versus temperature, and by the existence of an induced anisotropy. The various shapes of the loops are given and discussed. It is further shown why materials with Perminvar effect exhibit a specific evolution of the minor hysteresis loops with temperature changes, and the results obtained by Michalowsky are discussed.