Limits of metastable epitaxy: The structure of ultrathin Fe films onCu3Au(100)

Abstract

The influence of epitaxial strain on the structure of thin films was investigated using a model system: Fe on Cu 3 Au(100). Low-energy electron diffraction ͑LEED͒ I(V) measurements and full dynamical I(V) calculations were used to determine the atomic structures of Fe films at different thicknesses ͑3.3, 4.8, 18, and 53 monolayers ͑ML͒. LEED measurements show that for thicknesses above approximately 1.5 ML iron films are no longer pseudomorphic. Between 3.3 and 4.8 ML, the Fe films were determined to have a strained bcc structure, rather than the previously proposed fcc structure. The existence of the strained bcc phase at low coverage is consistent with estimates of the total energy, which suggests that the energy gained by stabilizing the bulk ground state of Fe overcompensates the higher strain energy of the bcc phase. At higher film thicknesses, 18-53 ML, dynamical LEED I(V) analysis confirm that the film structure has evolved into the expected unstrained bcc structure of Fe. ͓S0163-1829͑98͒01932-8͔

Ab initiocalculation of phase boundaries in iron along the bcc-fcc transformation path and magnetism of iron overlayers

“…3͑a͒, and our theoretical point is within the experimental limits. The other one 27 is somewhat shifted from the Cu 3 Au line. The structure of the films corresponds again to a tetragonally strained FM bcc phase, in agreement with experiment.…”

“…The structure of the films corresponds again to a tetragonally strained FM bcc phase, in agreement with experiment. 27 Fe films on Cu 84 Al 16 (001) are reported to be fcc with the volume of 12.15 Å 3 . 28 The corresponding point lies very close to the phase boundary between the FM and AFMD ordering in the fcc region.…”

Initial stages of growth of Fe onCu3Au(001)at low temperature: Formation of two-layer-thick islands

“…4,5,7 Concerning specifically the magnetic measurements, it is interesting to observe that the two experiments available on the magnetization of films deposited at LT are in substantial agreement about the onset (ϳ1 LE͒ of the hysteretic behavior in Kerr measurements. 7,4 Above this coverage the film shows a magnetization perpendicular to the surface; the saturation values of the magnetization increase linearly up to a critical thickness s where a spin reorientation transition takes place ͑the magnetization switches in a plane parallel to the surface͒.…”

“…[3][4][5][6][7] Previous studies on this system mostly focused on the properties of films grown at room temperature ͑RT͒. These studies report a scenario in which structural, morphological, and magnetic properties show a complex mutual relation.…”

Pseudomorphic-to-bulk fcc phase transition of thin Ni films on Pd(100)

“…As an example, the bulk structure of Fe deposited on Cu 3 Au(100) (where the 7% lattice mismatch is even smaller than the present one) is not fully recovered even for film thickness of the order of hundred of monolayers. 19,20 …”