Limitations of the Magneto-Optic Kerr Technique in the Study of Microscopic Magnetic Domain Structures

After considering the various factors that limit the performance of the Kerr technique in the observation of magnetic domains, it is concluded that the ellipticity caused by metallic reflection is of major importance. A detailed calculation of this effect is carried out, including the case of normal incidence. It is theoretically found that, for microscopic observation of magnetic domains using the longitudinal Kerr effect, the contrast is practically independent of the angle of incidence, and that there is an upper limit to the resolution obtainable, which is a function of the minimum contrast needed for observation. This resolution is usually of the order of a few microns. A detailed description of a Kerr instrument designed for microscopic observations is included.