Electronic and spectral properties of clean and C60-covered atom-thick Chromium oxide at the Fe(001) surface

*Guido Fratesi (1), Simona Achilli (1,2)
(1) ETSF and Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16, I-20133 Milano, Italy, (2) Currently at Catalan Institute of Nanoscience and Nanotechnology, Barcelona, Spain

Chemisorption of a single atomic layer of oxygen on the Fe(001) surface yields a highly ordered and reproducible benchmark substrate [1] for theoretical and experimental studies, and for the epitaxial growth of metal oxides, including atom-thick CrxOy layers, and hybrid interfaces with foreseen applications e.g. in organic spintronics.

This talk initially presents ab initio investigations that have supplemented microscopy and spectroscopy experiments of the electronic and magnetic properties of two-dimensional Chromium oxides of Cr3O4 and Cr4O5 stoichiometry grown on Fe(001), featuring antiferromagnetic magnetic configurations with underlying Fe(001) [2,3]. Despite Cr / CrO systems are notoriously difficult for mean field approaches, generalized-gradient results are found to explain most experimental findings, with a rigid shift of oxygen bands accounting for electronic correlation effects.

We eventually consider the effect of inserted Cr4O5 layers at the interface between the prototypical C60 organic semiconductor and Fe(001), which is shown to enhance the magnetic hybridization between the molecule and the surface through x-ray magnetic circular dichroism (XMCD) [4,5]. By means of ab initio calculation we characterize the local interface morphology, the magnetic configuration of the surface and the induced spin dependent electronic properties of the molecule, the latter reflecting the magnetic electronic properties of the surface at the relevant energy range. As seen from the substrate, adsorbates can influence the magnitude and even orientation of surface Cr magnetic moments. The interest in this interface is then twofold: on one side the thin magnetic oxide allows tailoring the magnetic properties of the organic layer, on the other side the adsorption of C60 can be envisioned as a tool to control the magnetic ordering of Cr atoms at the interface.

[1] A. Picone, M. Riva, A. Brambilla, A. Calloni, G. Bussetti, M. Finazzi, F. Ciccacci, L. Duò, Surface Science Reports 71, 32 (2016).

[2] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M. I. Trioni, L. Duò, F. Ciccacci, and M. Finazzi, Phys. Rev. B 87, 085403 (2013).

[3] A. Calloni, G. Fratesi, S. Achilli, G. Berti, G. Bussetti, A. Picone, A. Brambilla, P. Folegati, F. Ciccacci, and L. Duò, Phys. Rev. B 96, 085427 (2017).

[4] A. Brambilla, A. Picone, D. Giannotti, A. Calloni, G. Berti, G. Bussetti, S. Achilli, G. Fratesi, M. I. Trioni, G. Vinai, P. Torelli, G. Panaccione, L. Duò, M. Finazzi, and F. Ciccacci, Nano Lett. 17, 7440 (2017).

[5] A. Brambilla, A. Picone, S. Achilli, G. Fratesi, A. Lodesani, A. Calloni, G. Bussetti, M. Zani, M. Finazzi, L. Duò, and F. Ciccacci, Journal of Applied Physics 125, 142907 (2019).