Electronic and magnetic structure of a Cr monolayer on Ag(100).

Abstract

Angle-resolved photoemission is used to study the electronic structure of the Cr layers obtained by condensing one layer equivalent (LE), or less, of Cr on Ag(100) at low (\ensuremath{\sim}0.5 LE/min) deposition rates. The data confirm our earlier finding that, upon deposition on a mildly (\ensuremath{\sim}440 K) heated substrate, layer-by-layer growth takes place up to 1 LE, i.e., an ordered flat Cr monolayer with a good degree of perfection is formed. The substrate temperature during deposition is critical since lower (\ensuremath{\sim}300 K) or higher (\ensuremath{\sim}500 K) temperatures result in an inhomogeneous rough Cr layer. For the ordered flat monolayer the characteristic two-dimensional dispersion of the Cr 3d energy bands and their symmetry at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} is determined. It is argued that when considered together with electron-diffraction observations, which reveal a weak c(2\ifmmode\times\else\texttimes\fi{}2) pattern at low energies (\ensuremath{\le}30 eV), the photoemission results provide compelling evidence of a monolayer stabilized by antiferromagnetic order. The large energy gap at the Fermi energy indicates that the effect must be very strong with a local moment in the range (3--4)${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, as predicted theoretically.