Growth of Single Crystal Fe$_{1-x}$Ga$_{x}$ Thin Films*

Fe$_{1-x}$Ga$_{x}$ alloys are of recent interest because of their magnetostrictive properties. In bulk form these materials display cubic magnetic anisotropy. We have grown single-crystal thin films of Fe$_{1-x}$Ga$_{x}$ of various alloy concentrations using Molecular Beam Epitaxy (MBE). We find that the films display either a conventional (bulk-like) cubic magnetic anisotropy or a uniaxial anisotropy on top of an underlying cubic anisotropy. A Gallium dependent uniaxial anisotropy is introduced by growing the films on GaAs(001) or ZnSe/GaAs(001) substrates. Alternatively, films which show purely cubic magnetic anisotropy have been produced by growing the films on MgO(001) substrates. Thin film Fe$_{1-x}$Ga$_{x}$ alloys can be grown with much higher content of Gallium than bulk while preserving BCC crystal structure. Reflection High Energy Electron Diffraction (RHEED) performed during growth as well as post-growth magnetic anisotropy measurements will be discussed. Growth parameters and a mechanism for the observed uniaxial anisotropy that is consistent with each of the substrates used will be discussed.