Influence of Ga content on structure and anomalous Hall effect of Fe$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$ thin films on GaSb(100)

The Fe-Ga alloys have recently attracted great interests because they exhibited ferromagnetic properties with high Curie temperature, high saturation magnetization and unique magnetostriction properties which are promising to real applications such as actuators, acoustic sensors, torque sensors, and positioning devices in particular for micro and nano-electromechanical systems and the integrated magnetostrictive devices. Recently, electrical spin injection from Fe$_{\mathrm{0.5}}$Ga$_{\mathrm{0.5}}$ produces an electron spin polarization above 70{\%} on GaAs(001). However, the out-of-plane saturation field and magnetization decrease rapidly with Ga content. The Fe$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$ thin films (x$=$0.4,0.5) have been grown on GaSb(100) substrate using MBE. An epitaxial film with bcc $\alpha $-Fe crystal structure (A2) was observed in Fe$_{\mathrm{60}}$Ga$_{\mathrm{40}}$ film, while an impure Fe$_{\mathrm{3}}$Ga phase with DO$_{\mathrm{3}}$ structure appeared in Fe$_{\mathrm{0.5}}$Ga$_{\mathrm{0.5}}$ film. The saturated magnetizations are 570emu/cm$^{\mathrm{3}}$ and 180emu/cm$^{\mathrm{3}}$ and the coercivities are 170 and 364Oe at room temperature for Fe$_{\mathrm{0.6}}$Ga$_{\mathrm{0.4}}$ and Fe$_{\mathrm{0.5}}$Ga$_{\mathrm{0.5}}$, respectively. A hysteresis trend in Hall resistance vs. magnetic field was observed for Fe$_{\mathrm{0.5}}$Ga$_{\mathrm{0.5\thinspace }}$film. However, there is a weak hysteresis in Fe$_{\mathrm{0.4}}$Ga$_{\mathrm{0.6}}$ film.