Single-crystal (100)Fe films 90–330 Å thick have been grown on etch-annealed (100)GaAs substrates by molecular-beam-epitaxy techniques. Ferromagnetic resonance data indicate that the two in-plane 〈110〉 directions are inequivalent and, together with magnetometry data, show that the average film magnetization decreases as the thickness decreases. The inequivalence is attributed to the nature of the interface bonding at a (100) zinc-blende surface. The decreased magnetization is attributed to the formation of Fe2As microclusters in the film due to As diffusion which is supported by Auger and electron diffraction studies. In general, the Fe films grown to date on etch-annealed (100)GaAs substrates are significantly inferior to those grown on (110)GaAs.

Single-crystal Co2MnGe Heusler alloy films were epitaxially grown on GaAs (001) substrates by molecular beam epitaxy. In situ reflection high-energy electron diffraction patterns and Auger spectroscopy confirmed the high-quality growth and stoichiometry. At 5 K, a saturation magnetization of 1000 emu/cm3 was measured. In-plane ferromagnetic resonance shows narrow linewidths and four-fold plus uniaxial anisotropy. A room-temperature resistivity of 115 μΩ cm has also been determined. The temperature dependence of the resistivity shows metallic behavior down to low temperatures.

Molecular beam epitaxy methods have been used to grow good quality magnetic single-crystal films of bcc Fe on fcc GaAs substrates. These films were characterized by Auger, reflection high energy electron diffraction (RHEED) and ferromagnetic resonance (FMR) techniques. Both RHEED and FMR indicate that the best crystal quality occurs for substrate temperatures in the 175–225 °C range. For 200-Å films the Fe surface lattice constant agrees with that of bulk α-Fe.

Single-crystal {110} Fe films, grown for the first time by molecular beam epitaxy on GaAs, have been studied by a variety of techniques in order to determine the dependence of the magnetic properties upon film thickness L and quality, and an overview of these results is presented. The dependence of the ferromagnetic resonance (FMR) field upon its orientation in the (11̄0) plane was measured at 16.4 GHz and shows that the magnetically easy axis is [110] for L<50 Å and [001] for L≳150 Å. A theory of FMR which incorporates magnetocrystalline surface anisotropy is outlined. It successfully interprets the thickness dependence of the FMR data in the ultrathin (L≲50 Å) regime and shows them to be surface dominated. FMR data at 9.2 GHz, which contain both aligned and nonaligned resonance branches, are presented as a function L. In addition, the dependence of the branches on frequency f for 8 GHz<f<40 GHz along [001] and [110] are discussed.

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