Mossbauer effect study of face-centered-cubic-like Fe on Cu(001)

Epitaxial face-centered-cubic (fcc)-like Fe films have been investigated in situ in ultrahigh vacuum by Fe-57 conversion-electron Mossbauer spectroscopy (CEMS). A broad distribution of hyperfine magnetic fields, P(B-hf), With an extrapolated most-probable field of 32(2) T at magnetic saturation has been observed in similar to 3 monolayers (ML) thick films grown at similar to 90 or 300 K, and in similar to 7 ML thick films grown at similar to 90 K. Such films are in a ferromagnetic high-spin state. Their local structure is characterized by an electric quadrupole interaction, eQV(ZZ)/4, of + 0.114 +/- 0.05 mm/s from which we infer an anisotropically expanded fee (fct-like) structure with c/a approximate to 1.06. Approximately 5-7 ML thick films grown at 300 K are observed to be in a low-spin antiferromagnetic state below T-N similar to 70 K, and are fee (c/a = 1) above T-N. Site-selective CEM spectra taken on such films provide direct evidence for a magnetically ''live'' surface layer. The fcc-->bcc transformation occurring in 35 ML thick films deposited at 300 K was observed to be incomplete. (C) 1996 American Institute of Physics.