Short-period oscillations in photoemission from thin films of Cr(100)

Angle-resolved photoemission (PE) study of thin films of Cr grown on Fe(100) reveals thickness-dependent short-period oscillations of the PE intensity close to the Fermi energy at ${\mathbf{k}}_{\Vert }\sim 0$. The oscillations are assigned to quantum-well states (QWS) caused by the nesting between the Fermi-surface sheets around the $\Gamma$ and the $X$ points in the Brillouin zone of antiferromagnetic Cr. The experimental data are confirmed by density-functional calculations applying a screened Korringa-Kohn-Rostoker Green’s function method. The period of the experimentally observed QWS oscillations amounts to about 2.6 monolayers and is larger than the fundamental 2-monolayer period of antiferromagnetic coupling in Cr.

Figure 1

(Color online) Normal-emission PE spectra of $\mathrm{Cr}∕\mathrm{Fe}∕\mathrm{W}\left(100\right)$ taken at various Cr thicknesses. The dashed lines are guides to the eye to follow the BE changes of the features, which were obtained by a least-squares fit of the spectra.

Figure 2

Binding energies of features $A$ and $B$ as function of Cr deposition. Dotted vertical lines mark a 2.6-ML period of oscillations. The variation of the surface local density of states at the Fermi energy $({\mathbf{k}}_{\Vert }\sim 0)$ is shown in the lower panel.

Figure 3

Spin-dependent LDOS at the topmost Cr layer for 1-ML (dashed) and 2-ML (solid) Cr coverages The spin directions are defined with respect to the Fe substrate (arrows). The upper (lower) panel shows the local majority (minority) spin projections.

Figure 4

Spin-majority surface LDOS $({\mathbf{k}}_{\Vert }\sim 0)$ for 1 to 10 ML of Cr on $\mathrm{Fe}∕\mathrm{W}\left(100\right)$. The solid and dashed lines are used for odd and even numbers of ML. QWS for 4-ML coverage are shaded. The spin-minority surface LDOS for 1 and 5 ML of Cr are shown in the bottom. The left inset represents oscillations of the $\mathbf{k}$-integrated (dashed) and $\mathbf{k}$-resolved (solid) surface LDOS at $E_F$. The right inset demonstrates a calculated FS cut within the BZ of AF Cr. The solid line with arrows denotes a nesting vector $({\mathbf{k}}_{\Vert }\sim 0)$.