Exchange Coupled Double Layers for Magneto-Optical Applications

Optical data storage is a rapidly developing technique, which emerges in many varieties. Magneto-optical recording, in particular, applies amorphous rare earth/transition metal films, where a binary coded information is written thermomagnetically and is read by the magneto-optical Kerr or Faraday effect. To increase the writing speed and the recording density, techniques for direct overwrite and magnetically induced superresolution were proposed, which involve these of exchange coupled double layer systems as a storage media. In this paper, the principles and the properties of exchange coupled double layers are discussed with respect to the direct overwrite and the magnetically induced superresolution processes. A formalism based on a switching field diagram is developed yielding all information necessary to achieve reliable and practical writing procedures. As an example, the direct overwrite capability is demonstrated experimentally in antiparallel coupled layer systems.