Enhanced Fe 3dspectral weight near the Fermi level in Fe overlayers on Cr

Electronic structures of Fe on Cr (Fe/Cr) and Cr/Fe/Cr sandwich films, with an Fe coverage of 1--20 {}, have been investigated by using photoemission spectroscopy (PES). The Fe 3d partial spectral weight in Fe/Cr has been extracted as a function of the Fe overlayer thickness. Experimental results are compared with supercell band-structure calculations for a system with monolayer (ML) Fe on each side of five-layer Cr, Fe(1 ML)/Cr(5 ML)/Fe(1 ML), by using the linearized muffin-tin orbital band method. For a very thin Fe overlayer, very interesting features are observed: (i) a sharp emission just at EF, and (ii) two other structures at higher binding energies which resemble the Cr 3d valence bands. The former feature is expected to originate primarily from hybridization between Fe and Cr 3d electrons at the Fe/Cr interface, and partially from the Fe 3d surface states in the Fe overlayer. The latter features also suggest large hybridization between Fe and Cr 3d states at the Fe/Cr interface, as confirmed by band-structure calculations. The trends observed in PES measurements are qualitatively consistent with those in band-structure calculations for the Fe(1 ML)/Cr(5 ML)/Fe(1 ML) system. This work suggests the importance of electronic structures, such as Fermi surface effects, in determining the character of the exchange coupling as well as the magnitude of magnetoresistance in the Fe/Cr superlattice