Abstract
Fe100–xAlx (x = 0, 4, 10, 20, 30 at. %) alloy films of 40 nm thickness are prepared on MgO(001) single-crystal substrates by varying substrate temperature from room temperature to 600 °C. Single-crystal films of (001) orientation with bcc-based disordered A2 structure are obtained for the Al content range of x = 0 - 20 at. %. An ordered phase of DO3 structure is observed in Fe70Al30 films prepared at temperatures higher than 200 °C, whereas (001) oriented single-crystal films of A2 structure are obtained when prepared at room temperature. The film surface profile does not depend much on the film composition, while the surface roughness increases with increasing substrate temperature. Island-like crystals are observed for films prepared at 600°C for all compositions. Difference in lattice spacing measured parallel and perpendicular to the substrate is noted for the single-crystal thin films and it increases with increasing Al content. The lattice strain in single-crystal film is caused possibly to accommodate the lattice mismatch with the MgO substrate. The (001)-oriented single-crystal films with A2 structure show four-fold symmetries in in-plane magnetic anisotropy with the easy magnetization axis A2[100] and the hard magnetization axis A2[110], whereas the films with DO3 ordered structure show almost isotropic magnetic properties.
Highlights
Iron-based soft magnetic alloy materials, Fe-X (X = Al, B, C, Co, Ni, Si, etc.), with high saturation magnetization and high permeability values have been used as the core materials for transformers, electro-magnets, and electric motors
The reflection high-energy electron diffraction (RHEED) patterns for Al composition (x) up to 20 at.% agree with those from bcc(001) single-crystal of A2 structure, though the reflection spots from the samples deposited at room temperature (RT) are lacking sharpness, suggesting that crystal lattice distortions are included in the A2 structure
At RT, the pattern is similar to that from bcc(001) single-crystal but with spotty and ring-like contrast, suggesting that the film is not a perfect single-crystal. It changes to streaky with other reflections that are clearly recognized in the RHEED pattern of sample prepared at 400 ◦C which seems to have caused by a presence of DO3 ordered phase
Summary
Iron-based soft magnetic alloy materials, Fe-X (X = Al, B, C, Co, Ni, Si, etc.), with high saturation magnetization and high permeability values have been used as the core materials for transformers, electro-magnets, and electric motors. These materials have been used in a form of thin film in various applications such as micro-machines, magnetic recording heads, magnetic sensors, high-frequency signal filters, etc. There are some references on the structural and magnetic properties of polycrystalline Fe-Al magnetic thin films, there are few available reports on the preparation of Fe-Al single-crystal films
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