Use of the longitudinal magnetooptical Kerr effect to study non magnetic/magnetic bilayers.

We report the results of longitudinal magnetooptical Kerr effect (LMKE) measurements on bilayers consisting of a thick permalloy film covered by varying thicknesses of Nb. The LMKE pertains to a situation in which light with a finite angle of incidence is reflected from a plane surface, and M vector in the sample is parallel both to the plane of incidence and the surface. Either s- or p- linearly polarized 6328angstrom light is incident on the sample at 60degrees to the normal. The two components of the complex Kerr rotation are measured with a modulation technique utilizing a lambda / 4 plate and a Faraday rotator driven by dc and 2000 Hz signals. With cycling of an in-plane magnetic field, square magnetooptical hysteresis loops are observed in both rotation and ellipticity.