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.
Ni thin films were prepared on Al 2 O 3 (11 2 20) and Al 2 O 3 (0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy (UHV-MBE). The film growth structure and the magnetic properties were investigated. Ni epitaxial thin films with Ni(111) and Ni(100) planes parallel to the substrate surface are obtained on Al 2 O 3 (11 2 20) substrates, whereas Ni polycrystalline films grow on Al 2 O 3 (0001) substrates. The Ni(111) film formed on Al 2 O 3 (11 2 20) substrate consists of two types of domains whose orientations are rotated around the film normal by 30 each other. The magnetic properties of Ni films grown on Al 2 O 3 substrates are influenced by the magnetocrystalline anisotropy and the shape anisotropy caused by the roughness of Ni islands which form the Ni thin films. The relationships between the film structure and the magnetic properties are discussed.
FeCo thin films were prepared on MgO(100), MgO(110), and MgO(111) single-crystal substrates by UHV-MBE. The effects of substrate orientation and substrate temperature on the film growth structure and the magnetic properties were investigated. FeCo thin films with (100)bcc, (211)bcc, and (110)bcc planes parallel to the substrate surface grew epitaxially on respective MgO substrates. FeCo(100)bcc single-crystal films were obtained on MgO(100) substrates. FeCo(211)bcc bi-crystalline films grew epitaxially on MgO(110) substrates with two types of domains whose orientations were rotated around the film normal by 180 degrees with respect to each other. FeCo(110)bcc thin films grew epitaxially on MgO(111) substrates with two type variants namely, the Nishiyama-Wasserman and Kurdjumov-Sachs relationships. Atomically sharp boundaries were recognized between the FeCo thin films and the MgO substrates, where misfit dislocations were introduced in the FeCo thin films, presumably to decrease the lattice misfits. A 0.3% reduction of the lattice spacing normal to the substrate surface was observed for an FeCo thin film prepared at a substrate temperature of 100 °C. The lattice spacing reduction decreased with increasing substrate temperature. The magnetic properties of FeCo thin films grown on MgO substrates were nfluenced by the magnetocrysta i which form the FeCo thin films.
FeCo thin films were prepared on SrTiO3(100), SrTiO3(110), and SrTiO3(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 SrTiO3 substrates at elevated temperatures with different crystal growth orientations. The nucleation and growth process of FeCo thin films on SrTiO3 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 SrTiO3(100) substrates at 500 °C. FeCo epitaxial thin films with (110)A2 and (211)A2 planes parallel to the substrate surface are obtained on SrTiO3(110) substrates. FeCo thin films epitaxially grown on SrTiO3(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/SrTiO3(111) interface. The lattice constants of Fe50Co50 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 SrTiO3 substrates are influenced by the magnetocrystalline anisotropy and shape anisotropy caused by the roughness of FeCo islands that form the FeCo thin films.
Ni thin films were prepared on MgO(100), MgO(110), and MgO(111) single-crystal substrates in the temperature range between 100 and 500 °C by UHV-MBE. The growth process, surface morphology, and magnetic properties were investigated. Ni epitaxial thin films were obtained with different film growth orientations depending on the substrate crystal. When Ni films were deposited on MgO(100) substrates, RHEED reflection from hcp-Ni(112 _ 0) crystal was observed. However, X-ray diffraction analysis of the samples indicates that the resulting film structure is fcc-Ni(100), suggesting that the hcp-Ni(112 _ 0) is metastable and that most of the film has been transformed into a more stable fcc structure. In contrast, Ni epitaxial thin films with (110)fcc and (111)fcc planes parallel to the substrate surface were obtained on MgO (110) and MgO (111)
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