High exchange bias field induced in ferrimagnetic bilayers of amorphous rare earth-transition-metal alloys

The magnetic reversal processes of exchange-coupled double layers (ECDL) an d corresponding single layers of rare-earth-transition metal were studied b y magneto-optical Faraday rotation (FR). The dependence of FR on the temper ature shows a transition of DyFeCo/TbFeCo ECDL from one type to another nea r the compensation temperature of single layers. Minor and major hysteresis loops allowed us to measure the exchange bias field induced by DyFeCo, whi ch has also been calculated with an analytical model. We have also observed that an unusual hystersis loop appears few celsius degrees before this tra nsition occurs. In this letter, we analyze and describe different magnetiza tion states, and various kinds of magnetization processes, including the us ual and unusual FR loops, are explained in detail. (C) 1999 American Instit ute of Physics. [S0003-6951(99)01628-9].