Exchange coupling in nanocomposite FePtB thin film magnets

Abstract

The nature of coupling among the $L{1}_0$ FePt hard and ${\mathrm{Fe}}_x\mathrm{B}$ $(x=2,3)$ soft magnetic phases in FePtB nanocomposite thin film magnets is investigated by measuring the hysteresis loops and $\delta M$ (Henkel) plots. The FePtB thin films deposited under optimized sputtering conditions are shown to have almost fully exchange-coupled soft and hard magnetic phases, which resulted in good hard magnetic properties [in-plane $H_c\sim 604\mathrm{kA}∕\mathrm{m}$ and ${\left(BH\right)}_{\max }\sim 95.6\mathrm{kJ}∕{\mathrm{m}}^3$ ].