Spin and orbital configuration of metal phthalocyanine chains assembled on the Au(110) surface

Abstract

The spin and orbital configuration of magnetic metal phthalocyanines (MPcs) deposited on metallic substrates are strongly influenced by the rehybridization of the molecular states with the underlying metal. FePc, CoPc, and CuPc isolated molecules are archetypal systems to investigate the interrelationship between magnetic moments and orbital symmetry after deposition on a metallic substrate. MPcs form long-range ordered chains self-assembled along the reconstructed channels of the Au(110) surface. X-ray magnetic circular dichroism from the L-2,L-3 absorption edges of Fe, Co, and Cu shows that the orbital and spin configuration are strongly modified upon adsorption on the Au(110) surface if the orbitals responsible of the magnetic moment are involved in the interaction process. The magnetic moment for a single layer of molecular chains is completely quenched for the CoPc molecules, fully preserved for the CuPc and reduced for the FePc ones. The modified magnetic configuration is confined to the very interface layer, i.e., to the MPc molecules bound to the metal substrate up to the compact packing of the single layer. The different response can be rationalized in terms of the symmetry/orientation of the metal-ion d states interacting with the substrate states, as indicated by density functional theory calculations in agreement with experimental findings. DOI: 10.1103/PhysRevB.87.16540

Metal-phthalocyanine ordered layers on Au(110): Metal-dependent adsorption energy

“…The width of the interface core-level peak shown in the figures, which is mainly related to the m j splitting, is narrower (1 eV) than the width obtained for the fitted TF peaks. This feature is compatible with the general picture of charge transfer with change in the molecular spin state, 19 and consequently in the m j splitting, due to the interaction of Fe central atoms with Au. The interaction induces a strong reduction of the FePc magnetic moment values at the SL configuration suggesting a S = 1/2 configuration, as reported in Ref.…”

“…The interaction induces a strong reduction of the FePc magnetic moment values at the SL configuration suggesting a S = 1/2 configuration, as reported in Ref. 19.…”

“…The smaller width (1 eV) of the interface core-level peak with respect to the TF-components (1.4 eV) can be explained by a change in the spin state of the molecules at direct contact with the Au surface. 19 The presence of both the bulk-like and interface components for the Co-2p 3/2 corelevel at the CoPc/Au(110) system, along with the SL morphology shown in the STM image ( Fig. 1) suggest that the CoPc molecules assembled on Au(110) present comparable structural configuration and interaction process as the FePc molecules.…”

“…27 The Zeeman-like approach can be adopted thanks to the rather high spin-orbit splitting (13 eV), and to the orbital magnetic moment, as measured for FePc single layer adsorbed on Au. 19 Thus, we fit the Fe-2p 3/2 J. Chem. Phys.…”

“…15,16 The planar orientation, in particular for the first single-layer (SL), is due to an interaction between the metal-phthalocyanine orbitals and the Au electronic levels. [16][17][18][19] Transition metal phthalocyanines with an open shell structure of the central ion molecular orbitals, strongly interact with the metal substrates, affecting the electronic, optical, and magnetic properties of the organic/metal interface, thus influencing the performances of the molecular device. 10,20,21 In this paper, we determine the adsorption energy of FePc and CoPc adsorbed on Au(110), with respect to CuPc/Au(110), as estimated by Temperature Programmed Desorption (TPD).…”