Abstract
The determination of the atomic structure of a Mn monolayer deposited at room temperature on Ag(001) was achieved by using surface extended x-ray absorption fine structure. Keeping in mind the previous results of x-ray photoelectron diffraction, several structural models involving the two topmost layers of the Ag substrate were tested in ab initio polarization-dependent XAFS calculations. Among these models, the most consistent one with the experimental data is made of a mixture of two different local environments that correspond to two different structures: first an inverted layer of Mn atoms substituting Ag ones underneath the topmost plane in fcc Ag; second a surface alloy confined to the two topmost layers of Ag substrate. This latter arrangement corresponds to the observed low-energy electron diffraction long-range order. Accurate values for the Mn-Ag and Mn-Mn first interatomic distances were derived from standard analysis and found to be and respectively. This definitely establishes that, in this surface alloy, Mn adopts an unusually large atomic volume, essentially the same as Ag. This finding is consistent with a high spin state of the Mn similar to the one in dilute Ag-based alloys or in the atomic ground state.
- Received 23 December 1997
DOI:https://doi.org/10.1103/PhysRevB.57.15507
©1998 American Physical Society