Combinatorial electrodeposition of magnetostrictive Fe_1-x Ga_x

Alloys of iron and gallium were electroplated to produce magnetostrictive Galfenol Fe_1-x Ga_x (10<x<40 atom %) thin films. A trapezoidal Hull cell was used to control composition via a combinatorial approach where the deposition current density was varied predictably across the cathode. Four parameter spaces were identified in which metallic iron, Galfenol, oxide, and Ga-rich metal films, respectively, were produced. It was found that a broad range of current densities could be used to produce Galfenol by varying the concentration of Ga³⁺ and its complexing agent, sodium citrate, compared to that of Fe²⁺. A novel method employing energy dispersive X-ray spectroscopy (EDS) was used to determine thickness as well as composition at specific points along the cathode. Deposition rates, partial current densities, and deposition efficiencies were determined accurately as a function of current density using the Nohse equation. The EDS results were verified with Rutherford backscattering (RBS). As expected, deposition rates increased with current density, while efficiencies of codeposition decreased. The grain sizes and crystallographic orientations of metallic Galfenol were dependent on deposition rate with fast rates producing small grains of (110) texturing and slow rates primarily producing large (211) oriented cubic crystals.