Magnetic Domain Patterns on Single Crystals of Silicon Iron

Magnetic powder patterns have been obtained on electrolytically polished surfaces of single crystals of iron containing 3. 8 weight percent silicon. Domains are easily visible, outlined by accumulations of colloidal magnetic particles. Several techniques have been developed that enable the direction of magnetization in each domain to be determined. Many types of domain patterns are observed, depending on the orientation of the surface with respect to the crystal axes. The simpler patterns can now be interpreted in some detail, and support the idea that the internal domain structure is relatively simple and is usually composed of a series of plates or slabs magnetized at 45^ or 90^ to the plate length. In one case it is verified that the plate thickness depends on plate length in approximate accordance with theory; and, for the more complicated "tree" patterns, comparison of theory with experiment shows that good agreement can be obtained using theoretical values of the wall energy. Further verification of the theory of Bloch walls is obtained by determining from experiment the change in spin orientation on traversing the wall.