Structural and magnetic properties of FeRh films grown on MgO(0 0 1), MgO(0 1 1) and MgO(1 1 1) substrates

Abstract

FeRh thin films are grown on MgO(0 0 1), MgO(0 1 1) and MgO(1 1 1) single-crystal substrates at 600 °C by dc magnetron sputtering and post-annealed at the same temperature for 1 h. Effect of substrate orientation on structural and magnetic properties of FeRh films is studied using X-ray diffraction (Cu-Kα and synchrotron radiation), temperature, and field dependent magnetization measurements. FeRh(0 0 1), (1 1 2), (0 1 1) orientated films with CsCl ordering are obtained on MgO(0 0 1), MgO(0 1 1) and MgO(1 1 1) substrates, respectively. Epitaxial quality of FeRh(0 0 1) is relatively better than FeRh(1 1 2) and FeRh(0 1 1) films. The FeRh(0 1 1) film grows on two orientation relationships: Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS). Temperature-dependent out-plane XRD measurements indicate an increase in c-parameter ∼0.56% to 0.62% across the AF-FM phase transition. The c/a ratio indicate that FeRh(0 0 1) film has in-plane compressive strain, while FeRh(1 1 2) and FeRh(0 1 1) films have tensile strain. The c/a ratio and temperature-dependent magnetization measurements (M–T) indicate that AF-FM phase transition can be tuned by appx. 52 K (388 K to 440 K) by variation of lattice strain at FeRh/MgO interface. Thermal hysteresis of appx. 12.8 K, 17 K and 22.9 K is observed for FeRh(0 0 1), FeRh(1 1 2) and FeRh(0 1 1) thin films. Larger thermal hysteresis is expected due to relatively poor epitaxial quality of the FeRh(1 1 2) and FeRh(0 1 1) films as compared to FeRh(0 0 1) film. The larger remnant FM component is observed in nominal AF state (room temperature) in all the samples, and is expected due to combined effect of composition inhomogeneity, substrate-induced strain and defects.