MBE growth and magnetic behaviors in epitaxial Fe_100-xGa_x on SrTiO₃

Recently, Iron-gallium alloy (Fe_100-xGa_x with 0x30) is a promising material for magnetostrictive applications due to its high tetragonal magnetostriction ₁₀₀ at low magnetic field. Thus, we present understanding about structural and magnetic properties of disordered bcc-Fe crystal structure Fe_100-xGa_x (x = 10, 20, and 30) epitaxial thin films, grown on a piezoelectric SrTiO₃ substrate using molecular beam epitaxy. The lattice parameter increases with Ga alloying content, because the Ga atom's atomic radius is larger than the Fe atom's. The films showed metallic behavior with a decrease in electrical resistivity at room temperature with Ga content, due to the increase in carrier density. The room temperature saturation magnetization decreased, from 1575 to 991 emu/cm³ as Ga concentration increased from 10 to 30%. Interestingly, a two-step-hysteresis loop was observed in all samples. Magneto-optical Kerr images confirmed abnormal magnetic domain switching under an applied magnetic field. Specifically, the hysteresis loop of the film with a 10% Ga concentration reveals an obvious kink, whereas the loop of the film with a 30% Ga content is harder to see. As a results, it is possible to modify the magnetic properties of FeGa film by combining it with SrTiO₃, a complex ABO₃ perovskite oxide with a high piezoelectric constant. Our findings suggested that FeGa is a promising material for controlling magnetic anisotropy using a piezoelectric layer in magnetoelastic coupling devices.