Formation of B2-ordered FeRh alloy thin films on annealing of pure and nitrogen doped Fe/Rh multilayers

Abstract

Structural and magneto-transport properties of pure and nitrogen-doped FeRh alloy formed from thermal annealing of [Fe(36 Å)/Rh(41 Å)]20 and [FeN(36 Å)/Rh(41 Å)]20 multilayers have been studied as a function of annealing temperature (up to 750 °C). X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements are carried out to study the interdiffusion, alloy formation and phase analysis. From XRR studies, it is observed that intermixing initiates at 250 °C and the FeRh alloy phase is formed at 400 °C in both types of multilayers. Activation energy and diffusion coefficient values obtained from XRR indicate that diffusion is faster in pure Fe/Rh multilayers as compared to FeN/Rh multilayers. XRD measurements indicate the formation of the B2-ordered FeRh alloy phase at an annealing temperature (Tann) of 300 °C for pure Fe/Rh and at 400 °C for the nitrogen-doped FeN/Rh sample. PNR data at room temperature provides annealing-driven depth-dependent structures and magnetic depth-profiling at different annealing temperatures. Resistivity vs temperature (ρ-T) and magnetization (M−T) measurements shows a broad thermal hysteresis in both FeRh and nitrogen-doped FeRh alloy films. Room temperature magnetoresistance (MR) measurement shows a large negative MR of 32 % and 33 % for FeRh and nitrogen-doped FeRh alloy.