MAGNETIC DOMAIN-STRUCTURES OF RAPIDLY QUENCHED FE-CU-NB-SI-B ALLOYS OBSERVED BY LORENTZ MICROSCOPY

Magnetic domain structures of finely crystallized Fe73.5Cu1Nb3Si13.5B9 alloys have been studied by Lorentz microscopy. We found the size of the uniform area (du) having a locally uniform anisotropy strongly affects the domain structure and the associated magnetic properties. In the highest-permeability alloy annealed at 550°C, circularly magnetized domain patterns were observed. Since the domain-wall width (wd) is about five times as large as the area having a magnetic uniform anisotropy for the highest-permeability alloy (wd ∽ 5du), effects of the anisotropy field are averaged to zero, resulting in free movement of the domain wall. © 1990, The Japan Institute of Metals. All rights reserved.