FeCo epitaxial films were prepared on MgO(100), MgO(110), and MgO(111) substrates by ultrahigh vacuum molecular beam epitaxy. FeCo thin films with (100), (211), and (110) planes parallel to the substrate surface grow on respective MgO substrates. FeCo/MgO interface structures are studied by high-resolution cross-sectional transmission electron microscopy and the epitaxial growth mechanism is discussed. Atomically sharp boundaries are recognized between the FeCo thin films and the MgO substrates where misfit dislocations are introduced in the FeCo thin films presumably to decrease the lattice misfits. Misfit dislocations are observed approximately every 9 and 1.4 nm in FeCo thin film at the FeCo/MgO(100) and the FeCo/MgO(110) interfaces, respectively. X-ray diffraction analysis indicates that the lattice spacing measured parallel to the single-crystal substrate surfaces are in agreement within 0.1% with those of the respective bulk values of Fe50Co50 alloy crystal, showing that the FeCo film strain is very small. The magnetic anisotropies of these epitaxial films basically reflect the magnetocrystalline anisotropy of bulk FeCo alloy crystal.
Sm-Co thin films were prepared on Cu(111) single-crystal underlayers by changing the Sm composition from 12 to 35 at.% and the effects of Co/Sm composition on the ordered phase formation were investigated. The epitaxial SmCo 5 thin films were obtained for all samples. The SmCo 5 epitaxial layer grown on Cu underlayer has two different types of domains whose orientations are rotated around film normal by 30 degrees to each other. Cu atoms substitute a part of the Co sites in the SmCo 5 structure, and an alloy compound of Sm(Co,Cu) 5 phase was formed for all samples. The Sm(Co,Cu) 5 phase was more Cu enriched with increasing the Sm composition. The Cu atom diffusion into Sm-Co layer plays an important role in assisting the formation of Sm(Co,Cu) 5 ordered phase.Index Terms-Cu(111) single-crystal underlayer, epitaxial growth, ordered phase, SmCo 5 thin film.
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