We report epitaxial growth of body-centered cubic Fe and face-centered cubic Ni thin films on n-type AlGaAs͑001͒ substrates using electrochemical deposition with the cubic axes of Fe oriented parallel to the substrate lattice while the Ni is rotated in-plane 45°. The magnetic properties in either case are dominated by the fourfold crystalline anisotropy, a high remanence, and saturation magnetization values similar to bulk properties. The growth of such ferromagnetic contacts on AlGaAs might find applications in magneto-electronics.The discovery of spin-dependent transport 1-3 has recently stimulated wide interest in designs for memory and logic devices. In particular, the proposal of a spin-polarized field effect transistor 4 has triggered great attention on the issue of integration of ferromagnetic materials with semiconductors. Devices of this kind would require the growth of epitaxial ferromagnetic films with well-defined crystallographic, magnetic, and interface properties. Electrochemical deposition ͑ECD͒ in this regard offers important advantages as it is a low-energy, room-temperature deposition process which can limit the interdiffusion between the film and the substrate, thus enabling the growth of high-quality epitaxial layers. 5,6 In this article, we report on the electrochemical epitaxial growth of Fe and Ni films from sulfate electrolytes onto n-AlGaAs and on the structural and magnetic properties of the grown films. ExperimentalThe substrates were single-crystalline, n-doped GaAs͑001͒ on which a 200 nm thick Al 0.08 Ga 0.92 As:Si layer was grown by molecular beam epitaxy with 1 ϫ 10 18 cm −3 n-doping. The electrical contact to the substrate used for ECD was made using a Ga-In eutectic on the back side of the substrates. Prior to deposition, the substrates were cleaned in a 10% ammonia solution for 2 min and subsequently rinsed in deionized water prior to deposition. The surface area exposed for deposition typically was about 20 mm 2 .Electrodeposition was carried out under galvanostatic control ͑current density of 2.5 mA/cm 2 for Fe and 3.5 mA/cm 2 for Ni, using 0.1 M sulfate solutions with pH 2.5 in both cases͒ at 25°C in a prismatic cell with vertical parallel electrodes and a calomel reference electrode using a potentiostat EG&G, model 273A. In order to reduce the effect of any resistance variation of the back contact to the substrate, galvanostatic deposition was preferred over potentiostatic control. Graphite was used as the counter electrode. After deposition, the samples were rinsed with deionized water and blow dried. Film thicknesses are 50 nm for Ni and about 90 nm for Fe. These values were estimated from X-ray reflectivity for Ni and from saturation magnetic moments for Fe. Fe films were too rough to allow thickness measurements based on X-ray reflectivity. Hysteresis loops and angular remanence curves were measured using a Digital Measurement Systems vibrating sample magnetometer ͑VSM, DMS model 990͒. In-plane angular ferromagnetic resonance ͑FMR͒ was measured at 25.6 GHz with the dc fi...