Epitaxial growth of γ-Fe on Ni{001}

The epitaxial growth of Fe on Ni{001} is studied by means of low-energy electron diffraction (LEED) and Auger-electron spectroscopy (AES). Films thinner than about 4 atomic layers produce 1 × 1 LEED patterns and are found to be epitaxial, but with markedly expanded interlayer spacings. Films thicker than about 6 layers (up to 25 layers) produce 1 × 1 patterns with weak satellite beams that are attributed to the presence of bcc Fe{110} islands. A LEED analysis of the 1 × 1 component of a 10-layer Fe film reveals a body-centered tetragonal structure with bulk lattice parameters a = 2.489 Å (dictated by the Ni{001} substrate) and c = 3.88 Å (i.e., interlayer spacing dbulk = 1.94 Å, expanded 10% over the Ni spacing 1.76 Å). The first interlayer spacing d12 is expanded 5% with respect to the bulk. Strain analysis estimates that the equilibrium room-temperature lattice constant of the Fe phase grown in these experiments is 3.65 ± 0.04 Å, consistent with the results reported elsewhere for Fe films grown on Cu{001}. This information, combined with the results of total-energy band-structure calculations published elsewhere, shows that the γ-Fe phase grown in the present experiments is expanded with respect to the non-magnetic state, and has a strain that is slightly smaller in the ferromagnetic than in the antiferromagnetic state. © 1989.