Evidence of Coexistence of Ferromagnetic and Antiferromagnetic Phases in Nearly Equiatomic FeRh

Fe_100-xRh_x films were deposited on Si substrates with various Rh concentrations (conc.) (x) ~ 32 to 52% at. All the films showed the in-plane magnetic anisotropy due to the thin-film like structure i.e., shape anisotropy. For Rh conc. up to ~ 42% at., the films exhibit a single ferromagnetic (α\´) phase. However, for Rh conc. (x) > 42% at., there exists a mixture of ferromagnetic (α\´) and antiferromagnetic (α") phase. Nearly equiatomic samples ( x ~ 48 to 52% at.) showed abrupt enhancement in coercivity and a broad thermal hysteresis. This behavior is consistent with the presence of a mixture of FM and AFM phase. Thermal first-order-reversal-curves analysis showed that the AFM to FM phase transition is restricted to a region with FWHM of ~ T = 40 K, in spite of the mentioned broad thermal hysteresis.