Ferromagnetic: in ferromagnetic materials such as iron the magnetization can be much larger than that of para- or diamagnetic substances Domain: in ferromagnetic materials, there are re gions in which electron spins are aligned. the mag netization of one domain may be oriented at random w.r.t. that of a neighboring domain Remark: usually dielectric DX E, linear; but in ferromagnetic materials the magnetization is non linear and depends on history