Optical study of the coherence of Bloch walls motion during magnetization in Fe-Si 3% G.O. laminations

Through an optical technique making use of the Kerr effect, the motion of the Bloch walls on G.O. polycrystalline and single crystal Fe-Si strips is studied. The aim is to evidence the effects of internal fields on the wall motion, as produced by a driving field applied to the specimen. Results show that the motion of the walls in well oriented single crystal specimens is very little influenced by internal fields when displacements much larger then single Barkhausen jumps are taken into account. On the contrary, in polycrystalline G.O. specimens strong interaction effects arise, particularly in the low frequency components of the forced motion. Some implications of these results on the theory of the magnetic power loss are discussed.