Spin-polarized photoemission study of epitaxial Fe(001) films on Ag(001) (abstract)

Abstract

The electronic and magnetic character of epitaxial bcc Fe(001) films grown in situ on Ag(001) has been studied as a function of Fe coverage by spin- and angle-resolved photoemission (normal emission).1 The films were characterized with UPS, AES, and LEED, and a layer-by-layer mode of film growth was confirmed for the first 3 ml. We obtain good agreement with the calculated critical point energies2 at Γ for Fe coverages in the monolayer regime; however, we observe no net in-plane spin polarization up to 2.5 ml, even though an exchange-split electronic structure is inferred from the data. Although the initial calculations do not specify a direction for the moment, this is in apparent contrast with the prediction of an enhanced magnetic moment for one or two monolayers.2,3 The absence of polarization indicates that such films cannot be magnetized remanently along the in-plane 〈100〉 axis at room temperature. We conclude that a strong surface/film anisotropy favors the domain moments to lie along the surface normal up to 2.5 ml. Very recent anisotropy calculations for a free-standing Fe monolayer at the Ag lattice indicate that the easy magnetization axis is in fact perpendicular to the surface.4 A significant increase in emission intensity at EF of minority-spin origin accompanied by a net in-plane spin polarization is observed by 5.2 ml (the next coverage studied), suggesting a transition from surface dominated behavior to a bulklike character.