MAGNETOOPTICAL DOMAIN-WALL OBSERVATION AT PERPENDICULAR INCIDENCE

Domain wall configurations in soft magnetic materials are invisible in the regular polar magnetooptical Kerr effect at perpendicular incidence. Earlier we reported about two other contrast mechanisms under these conditions: the Voigt effect and the magnetooptical gradient effect. The net contrast from both effects vanishes for certain wall orientations relative to the polarization axis of the light; the case of a 180 degrees-waI1 oriented parallel to the E-vector of the light is an example. The weak ''residual'' contrasts observable under such circumstances are the subject of this paper. The residual contrasts have a dipolar character. They can be consistently analysed in terms of magnetooptical gradient and Voigt effect contributions due to the surface wall structure itself. The two contributions interfere constructively or destructively depending in a predictable fashion on domain magnetization.