Electronic structure of ultrathin γ′-Fe4N (100) films epitaxially grown on Cu(100)

The electronic structure of ultrathin films of gamma(')-Fe4N(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 gamma(')-Fe4N(100) surface is laterally heterogeneous and contains both areas reconstructed with a p4gm(2x2) 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(2x2)N/Fe(100) provides spectroscopic evidence that a subsurface excess of N drives the p4gm(2x2) reconstruction.