Signal Enhancement of Time-resolved Magneto-optic Measurements on Individual Nanomagnets

The sensitivity of magneto-optic Kerr measurements of nanomagnetic structures is significantly improved using cavity enhancement to increase the Kerr signal by depositing dielectric layers on the magnetic surface under study. We discuss different strategies to optimize the use of cavity enhancement for observation of nanomagnets. We show that maximization of the Kerr rotation from magnetic structures results in higher sensitivity for magnetic films, but does not yield the highest sensitivity for nanomagnets. Instead, the use of an anti-reflection coating on the substrate surrounding the magnet in conjunction with index optimization of the enhancement layer can increase the Kerr signal by more than two orders of magnitude in the deep nanometer range, and enables detection of individual nanomagnets using conventional far-field Kerr microscopy.