Electronic structure of ultrathin γ′ - FFe4 N (100) films epitaxially grown on Cu(100)

7 págs.; 11 figs.; PACS number s : 73.20. r, 71.20. b, 71.15.Mb, 68.37.EfThe electronic structure of ultrathin films of γ′ - Fe4 N (100) deposited on Cu(100) has been characterized by a combination of photoelectron spectroscopies, scanning tunneling microscopy, and diffraction techniques. The comparison of the data with first-principles simulations sheds light on magnetic moments, type of bonding, and charge transfer. N atoms residing in the bulk or at the surface are found to be distinguishable. The γ′ - Fe4 N (100) surface is laterally heterogeneous and contains both areas reconstructed with a p4gm (2×2) symmetry and bulklike terminated. The densities of states of the reconstructed and unreconstructed areas of the surface are obtained and compared with the experiment. Comparison with c (2×2) N Fe (100) provides spectroscopic evidence that a subsurface excess of N drives the p4gm (2×2) reconstruction. © 2007 The American Physical Society.This work has been supported by the Spanish CICyT under Grants No. FIS 2004-01026, No. MAT2004-05865, and No. NAN2004-08881-C02-01 and the Comunidad de Madrid under Grant No. S-0505/MAT-0194.Peer Reviewe