Methods of observing magnetic domains in electrical steels

For in-depth understanding and more accurate predictions of the performance of modern soft magnetic materials, particularly under a.c. magnetisation, the more complex structures present in real materials must be taken into account. This calls for methods of directly observing and quantifying static and dynamic domain structures. The following sections cover the most common domain observation techniques, roughly in chronological order of their first usage, which not surprisingly corresponds roughly according to their capability. These include powder techniques, optical methods such as the magneto-optical effect, magnetic force microscopy etc. They are all applicable for domain observation on any magnetic material but emphasis is placed on their relevance to electrical steels.