Domains, domain walls and the coercive field of amorphous ferromagnets

Magnetic properties of the hysteresis loop of magnetostrictive amorphous ferromagnetic alloys are predominantly determined by the magnetoelastic coupling energy between the spontaneous magnetization and internal stresses. Domain structures as well as the pinning of domain walls are governed by long-range and short-range stresses, respectively. As sources of elastic stresses we have detected quasidislocation dipoles exerting stress fields which vary as 1/r2. The coercive field is shown to be determined by four types of interactions : 1) volume pinning by stress sources; 2) intrinsic fluctuations of material properties; 3) surface irregularities; 4) relaxation phenomena.