Observation of Large Kerr Angles in the Nonlinear Optical Response from Magnetic Multilayers

We have observed a longitudinal nonlinear (second-harmonic) Kerr rotation up to 22° for an Fe(2 nm)/Cr(2 nm) multilayer on an Si${\mathrm{O}}_2$ substrate that shows a linear Kerr rotation of only a few hundreths of a degree. The latter value excludes any linearly induced mechanism and confirms the interface sensitivity of this nonlinear Kerr technique. The enormous enhancement is shown to be in good agreement with recent predictions, based on spin dependent band structure calculations. The local optical field effects are shown to play an important role for the additional enhancements for such multilayers on a substrate.