A FORMALISM TO DETERMINE THE DOW AND MSR CAPABILITY OF EXCHANGE COUPLED LAYER SYSTEMS

Abstract

The storage media for the magneto-optic (MO) recording technology available on the market today consist of thin ferrimagnetic films of amorphous rare earth/transition metal (RE/TM) alloys. Because the writing speed is limited by the need to erase entire sectors before writing new data, great effort has been made to develop direct overwrite (DOW) techniques, where the light intensity modulation technique appears to be the most promising method. This technique involves the use of exchange coupled layer systems as storage media. On the other hand, exchange coupled layer systems can also be used to increase the storage density without changing the optical arrangement introducing the so called magnetically induced superresolution process (MSR). Both methods, however, suppose a detailed knowledge of the switching behaviour of the exchange coupled films.Therefore, exchange coupled double layers (ECDLs) were produced and their magnetization reversal behaviour was analyzed yielding a characteristic switching field diagram for each investigated sample. Using this switching field diagram, a formalism was deduced, which enables to prove the DOW or MSR capability of exchange coupled layer systems using data only obtained from macroscopic investigations (Kerr measurements).