Combined spectroscopic and ab initio investigation of monolayer-range Cr oxides on Fe(001): The effect of ordered vacancy superstructure

Abstract

We investigated the electronic structure of an ultrathin Cr oxide film prepared by growing about 0.8 monolayers of Cr on the oxygen-terminated Fe(001)-p(1×1)O surface and characterized by the formation of an ordered array of Cr vacancies producing a ( √ 5× √ 5)R27• superstructure. We combined experimental techniques such as angle-and spin-resolved photoemission spectroscopy, low-energy electron diffraction, and scanning tunneling spectroscopy with ab initio calculations, focusing on (i) the peculiar energy dispersion of O 2p states and (ii) the orbital and spin character of Cr 3d states. We show that the experimental O 2p dispersion can be related to the presence of an ordered vacancy lattice. The comparison with the existing literature on the oxidation of bulk Cr(001), where a network of Cr vacancies with a short-range crystallographic order is present, reveals a similar effect on O states. The valence electronic structure of the Cr oxide layer is mostly composed by spin-minority Cr states, consistent with an antiferromagnetic coupling with the Fe substrate.

Effects of the introduction of a chromium oxide monolayer at the C60/Fe(001) interface

“…The two lowest panels show the antiferromagnetic alignment of Cr and Fe, while in the third one, the small spin polarization of oxygen atoms can be appreciated, as discussed in our earlier work. 16 Notably, the binding energy of the oxygenrelated features is in good agreement with the peak observed in the PES. The two upper panels of Fig.…”

“…The latter, which is related to oxygen states, is reminiscent of a similar peak that characterizes the PES spectrum of the Fe(001)-p(1 Â 1)O substrate (not shown here) as discussed in Ref. 16.…”

“…14 This system is characterized by a long-range FM order with in-plane magnetization, oriented anti-parallel with respect to that of the Fe substrate. 15,16 Fullerene films were grown onto the Cr 4 O 5 =Fe substrates by MBE under UHV conditions, with the substrates held at room temperature.…”

Room temperature magnetism of ordered porphyrin layers on Fe

“…2(b)] is characterized by a sharp peak at about À4.3 eV due to photoemission from O 2p-derived states and some small intensity signal from bulk Fe 3d states close to the Fermi energy (E F ). 40,41 Two spin-resolved features are visible on the corresponding IPES spectrum [ Fig. 2(b)], due to transitions toward the bulk majority and minority-spin empty states.…”

Tailoring the magnetic ordering of the Cr4O5/Fe(001) surface via a controlled adsorption of C60 organic molecules

“…In recent works [14][15][16] some of us focused on the C 60 /Fe(001) interface, both on the experimental and theoretical viewpoint. We demonstrated that the induced magnetic properties on the molecules depend on the spin polarization of the substrate states interacting with the molecule itself and by their decay toward vacuum.…”