FeCo thin films were prepared on SrTiO
3(100), SrTiO
3(110), and SrTiO
3(111) single-crystal substrates by ultra-high vacuum molecular beam epitaxy. The film growth structure and magnetic properties were investigated. FeCo epitaxial thin films are obtained on these SrTiO
3 substrates at elevated temperatures with different crystal growth orientations. The nucleation and growth process of FeCo thin films on SrTiO
3 substrates vary depending on the orientation of the substrate and its temperature. FeCo(100) single-crystal thin films with an
A2 structure are obtained on SrTiO
3(100) substrates at 500°C. FeCo epitaxial thin films with (110)
A2 and (211)
A2 planes parallel to the substrate surface are obtained on SrTiO
3(110) substrates. FeCo thin films epitaxially grown on SrTiO
3(111) substrates consist of two crystallographic phases having
A2 and hexagonal structures with the (110)
A2 and (0001)
hex planes parallel to the substrate surface. The metastable FeCo(0001)
hex plane is presumably formed in order to relax the strain caused by the lattice mismatch at the FeCo/SrTiO
3(111) interface. The lattice constants of Fe
50Co
50 crystal with the hexagonal structure are estimated to be
a = 0.251±0.004 nm and
c = 0.457±0.005 nm. The magnetic properties of FeCo epitaxial thin films grown on SrTiO
3 substrates are influenced by the magnetocrystalline anisotropy and shape anisotropy caused by the roughness of FeCo islands that form the FeCo thin films.
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