Experimental study of Bloch wall surface pinning in 3% Si-Fe monocrystalline lamination

Surface pinning of Bloch walls has important effects on the magnetization process of ferromagnetic laminations. For oriented materials it may be responsible for the largest part of the hysteresis loss, as shown by experiments made on laminations having different thickness. A new aspect of surface pinning concerns its influence on wall bowing and on the dynamic loss. The local excess loss generated by the surface Barkhausen jumps hinders the higher mobility of the wall near the surface predicted by the skin effect, and thus changes a few important conclusions about the behaviour of the dynamic loss when the magnetizing frequency is increased. In the present paper a study of the surface pinning is performed by means of an optical technique making use of the longitudinal Kerr effect and of two laser beams to apply cross-correlation analysis. Results about wall bowing and pinning field and the lamination surface are given.