Structure and magnetic properties of electrodeposited, ferromagnetic, group 3-d element films grown onto GaAs (011) substrate

Abstract

Ni, Co, and iron-rich FeNi films were grown onto n-GaAs (011) substrates using electrodeposition from metal sulfate solutions, at room temperature, with a current density of 3.5 mA/cm2 at a pH of 2.5. The structure of Ni film is found to be fcc with a (111) preferred orientation, whereas Co films show a mixed fcc and hcp structure that is confirmed by x-ray diffraction and transmission electron microscopy data. The structure of iron-rich (>90%) FeNi films remains unclear at the moment. The films show a well-defined, in-plane, uniaxial anisotropy with the easy axis along the [011] GaAs direction for Ni, and [011̄] GaAs direction for Co and FeNi films (i.e., anisotropy rotated by 90° compared to Ni). Co films maintain their anisotropy even for large thicknesses (>250 nm) and so does Ni (up to 90 nm). Surprisingly, thin Ni films exhibit a larger HK value (950 Oe) than what would be expected from a purely crystalline anisotropy. This effect is ascribed to internal stresses in the as-deposited films.