Electronic states and magnetism of ultrathin Fe/Cu/Si(1 1 1) films

Abstract

Epitaxial Fe/Cu/Si(1 1 1) ultrathin overlayers with Fe thicknesses ranging from 1 to 3 ML (monolayer) have been grown as well as a 30 ML thick iron film. The evolution of their electronic and magnetic properties next to the iron fcc–bcc structural transition has been investigated by using several UHV techniques and compared to experimental results obtained for a completely bcc Fe/Cu heterostructure. For fcc Fe coverages we found that at room temperature the magnetic moment, m, is nearly zero contrary to that obtained by local spin density calculations which reported for a surface iron layer an m value even higher than in the bulk. Our measurements of electronic density of states suggest that the ultrathin film exchange splitting is even lower than that of bulk iron contrary to what is expected by theory. The observed decrease of the exchange splitting is not sufficient to explain the macroscopic magnetic behaviour.