Thickness-dependent magnetic order and phase-transition dynamics in epitaxial Fe-rich FeRh thin films

The control of magnetic order and phase-transition dynamics by various means is a key towards low-power spintronics. Here, we report a control on magnetic order and phase-transition dynamics by tuning film thickness in epitaxial FeRh films. Reduction of film thicknesses from 200 nm to 5 nm results in an anti-ferromagnetic to ferromagnetic phase change, accompanied by a 0.55% lattice expansion for c-axis. The phase-transition dynamics is highly dependent on the film thickness, and involves the release and recovery of lattice strain that results in a lower transition temperature and larger thermal hysteresis in thinner films. The findings help to understand the origin of thermal hysteresis and phase-transition dynamics in ultra-thin FeRh films. Possible approaches to narrow down thermal hysteresis are proposed.