Evidence of chemical bonding in the electronic structure of a metastable Fe80Cu20 alloy

We studied the electronic structure of a metastable Fe80Cu20 alloy using x- ray photoelectron spectroscopy (XPS). The sample was produced by ball-milli ng, giving single-phase (BCC) nanoparticles with a diameter of about 10 nm. The core level Fe 2p and Cu 2p spectra of the alloy are rather similar to those of the individual Fe and Cu constituents; the absence of chemical shi fts in these spectra indicates that the charge transfer between the Fe and Cu is negligible. On the other hand, the valence band spectrum of the alloy deviates from a linear combination of the corresponding Fe and Cu bands. T he difference in the valence band of the alloy is attributed to bonding int eractions between the Fe 3d and Cu 3d states. This illustrates the presence of chemical bonding between the valence electrons in a metastable alloy ma de of immiscible elements.