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Epitaxy of Co on FeAl{001}. II. c (2×2) films

1994; American Physical Society; Volume: 49; Issue: 24 Linguagem: Inglês

10.1103/physrevb.49.17391

1095-3795

C. P. Wang, S. C. Wu, F. Jona, P. M. Marcus,

Magnetic Properties of Alloys

The c(2\ifmmode\times\else\texttimes\fi{}2) low-energy electron-diffraction (LEED) pattern observed on Co films thicker than about 13 \AA{} on FeAl{001} is shown to be caused by a strained hexagonal Co(112\ifmmode\bar\else\textasciimacron\fi{}0) film. The film is strained differently in the two orthogonal directions within the plane of the interface: it is expanded by 0.91% in one and compressed by 5.4% in the other direction. As a consequence, the bulk interlayer spacing, as determined by quantitative LEED, is expanded by 2.9% with respect to the spacing in the unstrained hexagonal-close-packed phase (1.2535 \AA{}). This is a more general case of pseudomorphic epitaxy than when film and substrate have similar unit meshes, and requires a more elaborate strain analysis. Such strain analysis finds an interlayer strain of 3.35%, in satisfactory agreement with the quantitative LEED result. It is noted that the strained Co(112\ifmmode\bar\else\textasciimacron\fi{}0) film does not grow directly onto the FeAl{001} substrate, but rather on a strained Co{001} film, 8--10 layers thick, which grows first on the substrate and is analyzed in a previous paper.