Kerr effect enhancement by photon tunneling and possible application to a new scanning probe magnetic microscope

Magneto-optical effects are calculated fur the film stack consisting of hem isphere glass/magnetic him (10 nm)/air gap (d nm)/glass plate. Polarized li ght (wave length = 800 nm) is irradiated through the hemisphere glass in th e total internal reflection configuration. A typical amorphous rare earth-t ransition metal alloy is used for the magnetic layer. We find a large monot onic change in the figure of merit (product of the reflected amplitude of l ight and the Kerr rotation angle) as a function of the air gap, ranging fro m 1 to 800 nm, Similar results are obtained for a magnetic film with a 10 n m SiO2 protective layer and for a 1-nm-thin magnetic film, This phenomenon is mostly caused by a change in the reflectivity at magnetic film/air inter face due to photon tunneling. The difference in the figure of merit between perpendicular and longitudinal magnetization is about 0.6 degrees. These r esults imply that it might be possible to obtain an image of perpendicular magnetic moment with photon scanning tunnel microscopy (STM), This method c an be combined simultaneously with a conventional atomic force microscope o r STM, (C) 1998 American Institute of Physics. [S0021-8979(98)53511-6].