Microscopic environment of Fe in epitaxially stabilized c-FeSi

Epitaxially stabilized iron monosilicide films having the CsCl structure (c -FeSi) have been investigated by conversion electron Mossbauer spectroscopy and transmission electron microscopy. The Fe-57 Mossbauer parameters (isom er shift delta, linewidth Gamma, and quadrupole splitting Delta) are report ed and discussed in terms of the local surrounding of the Fe nucleus. High statistical accuracy and resolution allowed a detailed investigation of the effects of strain and of the structural phase transformation from the epit axially stabilized to the bulk stable phase, The phase transformation was f ound to proceed in a rather surprising layer by layer mechanism with smooth interfaces between the epitaxially stabilized, the bulk stable, and a thir d phase. Results from a molecular-dynamics simulation at constant pressure and temperature of the structural phase transition are presented and compar ed with the experimental findings. The isomer shift and the electric-field gradient at the Fe nucleus in the strained c-FeSi and in the third phase ha ve been calculated using the ab initio full potential linear muffin-tin orb ital method. The Mossbauer parameters of some relevant point defects in c-F eSi have likewise been calculated within this framework. [S0163-1829(99)013 02-8].