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

The corresponding single layers of rare-earth-transition metal and the magnetic reversal processes of exchange-coupled double layers (ECDL) were studied by magneto-optical Faraday rotation (FR). The dependence of FR on the temperature shows a transition of DyFeCo/TbFeCo ECDL from one type to another near the compensation temperature of single layers. Minor and major hysteresis loops allowed the measurement of exchange bias field induced by DyFeCO, which has also been calculated with an analytical model. It was observed that an unusual hysteresis loop appears few celsius degrees before the transition occurs. Different magnetization states and various kinds of magnetization processes, including the usual and unusual FR loops are analyzed and described.