Magneto-optical observations of the surface reversal process in amorphous glass-coated microwires with positive magnetostriktion
Dr. Kornel Richter (Dept.of Phys., Univ. of Pavol Jozef Sararik in Kosice, Park Angelinum 9)

Amorphous glass-coated microwires are well-known by very high domain wall velocities that reach up to 18 km/s [1-2]. Despite a big attention paid to this phenomenon, its origin is still not so clear. It was shown previously that the domain wall propagating in axial domain of microwires strongly interacts with the shell of surface domain structure. This results in the surface magnetization change that was used to measure the domain wall velocity by use of magneto-optical Kerr-effect (MOKE) [3]. Here, we perform a detail study of such phenomenon via magneto-optical observations made by polarizing microscope. A detail analysis of the cylindrical sample observation is performed.
The magneto-optical observations of planar samples are usually performed by use of “s” or “p” polarized light in order to avoid a strong ellipticity of reflected light. However, this experimental condition cannot be fulfilled in the case of cylinders, where non parallel planes of incidence appear as a result of curved surface. A detailed calculation of magneto-optical contrast revealed that change in the axial magnetization of cylinder results in the black and white magneto-optical contrast that can be explained by the combination of longitudinal and transverse contributions to MOKE.
Once, the origin of magneto-optical contrast in cylinders was understood, the domain wall was trapped in a potential well. The observation confirmed the inclined shape of the domain wall, which can be found responsible for the apparent high domain wall velocities measured by Sixtus-Tonks method.