Specular and off-specular x-ray reflectivity data for 50 nm-thick FeRh thin films with Au cap grown at (a) 323 K after FeRh film annealing at 873 K (“cold Au”) and (b) Au cap grown at 873 K prior to FeRh annealing at 873 K (“hot Au”). The specular XRR fits, shown here, demonstrate goodness-of-fit values of ∼0.1 indicating a good agreement between the calculated and measured curves.
(00L) x-ray diffraction patterns, given in reciprocal lattice units (r.l.u), for the “cold Au” (solid squares) and “hot Au” (solid line) FeRh thin films.
(00L) x-ray diffraction patterns measured around the (002) Bragg reflection of the “hot Au” film at various temperatures during heating. The high temperature Bragg reflection at T = 424 K) corresponds to the FM phase and is fit with a double Pseudo-Voigt function. The “cold Au” (00 L) XRD patterns are not shown here.
Temperature dependence of the out-of-plane c lattice constant of Phase 1 (solid triangles) and Phase 2 (open triangles) in the “hot Au” FeRh film, upon heating to 424 K, and of the single phase in the “cold Au” (solid squares) FeRh film. The lattice parameter expansion of each phase in the “hot Au” film is found to be 0.14% and 0.6%, while the lattice parameter expansion of the phase in the “cold Au” film is ∼0.9%. Phase 1 in the “hot Au” film is considered as the more equiatomic FeRh phase.
Magnetization vs. temperature hysteresis loops, measured in a constant in-plane field, for (a) the “hot Au” and (b) the “cold Au” FeRh films.
Thermal hysteresis width as a function of applied magnetic field for the “hot Au” (open circles) and “cold Au” (closed squares) FeRh thin films.
Temperature derivative of magnetic moment for: the (a) heating branch and (b) cooling branch of “cold Au” FeRh film; and (c) heating and (d) cooling branches of the “hot Au” FeRh film. The inset of (d) shows a clear emergence of the secondary phase transforming upon cooling the temperature.
Plot of the magnetostructural transition temperature, T t as a function of applied magnetic field of the “hot Au” and “cold Au” FeRh thin films.
M vs H plots measured at 300 K for both the “hot Au” (closed squares) and “cold Au” (open squares) indicating retention of considerable ferromagnetism at room temperature.
Schematic of a simplified model of the “hot Au” and “cold Au” FeRh thin films of this study. The relative thicknesses and compositions listed in this schematic representation arise from the XRR data fitting results presented in Fig. 1.
Calculated composition, film thickness, and interfacial width values for both the “hot Au” and “cold Au” FeRh thin films based on the specular XRR fittings shown in Fig. 1; all thickness and interfacial width values are given in nm while compositions are listed in terms of at. %. Errors in the atomic compositions of the listed alloys are estimated at ±10% in the compositional variation and ± 0.5 nm in the thickness and surface interfacial width determinations.
Lattice constants and strain parameters of the “hot Au” and “cold Au” FeRh thin films. The c-lattice parameter values were measured for BCT FeRh by x-ray diffraction at 300 K, in the AF phase. Note: c-parameters are listed for each of the independent phases in the “hot Au” film. Strain values are derived from the experimental lattice parameter for bulk FeRh in the AF phase (as described in the Sec. II).
Transition temperatures (T t) and thermal hysteresis width (ΔT t) of FeRh films as a function of applied field obtained from magnetization measurements.
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