Study of exchange bias effect in a patterned Fe/Pt multilayer with the thermal annealing

Abstract

The present work reports the preparation of 5 μm wide and 10 μm grating periodicity patterned [Fe(2.0nm)/Pt(2.5nm)]X10 multilayer and its thermal annealing behavior. Intermixing across the Fe and Pt layers is observed with vacuum annealing at 650 K resulting in the formation of disordered face centered cubic (FCC) and ordered L10 face centered tetragonal (FCT) FePt phases. The longitudinal magneto-optical Kerr effect (L-MOKE) hysteresis loop, measured from the single 5 μm FePt stripe shows double loop behavior indicating the presence of two magnetic phases, one with the low coercivity (HC) and the second one with the higher HC values. This could be due to the presence of disordered FCC and ordered L10 FCT phases of FePt, known to be soft and hard magnetic phases. Conversion electron Mössbauer spectroscopy of the annealed sample shows the presence of FCC and FCT FePt phases corroborating the x-ray diffraction and MOKE measurements. The hysteresis loop of the soft phase shows the exchange bias effect with the remnant state of the hard magnetic phase as initial condition akin to the exchange bias as observed in conventional ferromagnetic - antiferromagnetic bilayers.