Enhanced Magnetism through Oxygenation of FePc/Ag(110) Monolayer Phases

Abstract

Iron-phtalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monolayer phases going from rectangular to different oblique phases, with increasing molecular density. We have investigated the oxygen uptake capability of the different phases and their associated magneto-structural changes. Our study combines scanning tunneling microscopy and spectroscopy (STM/STS), X-ray magnetic circular dichroism (XMCD), and density functional theory (DFT) calculations. STM measurements reveal that the oxidation reaction of the FePc/Ag(110) generally involves a displacement and a rotation of the molecules, which affects the electronic state of the Fe centers. The oxygen intercalation between FePc and the substrate is greatly obstructed by the steric hindrance in the high-density phases, to the point that a fraction of oblique phase molecules cannot change their position after oxydizing. Depending on the oxidation state and adsoption geometry, the STS spectra evidence clear differences in the Fe local density of states, which are mirrored in the XAS and XMCD experiments. Particularly, XMCD spectra of the oxidized phases reflect the distribution of FePc species (non-oxygenated, oxygenated-rotated and oxygenated-unrotated) in the different cases. Sum rule analysis yields the effective spin (ms eff ) and orbital (mL) magnetic moments of Fe in the different FePc species. Upon oxidation, the magnetic moment of FePc molecules increases about an order of magnitude, reaching mTOT~2.2 B per Fe atom.

Surface Deposition Induced Reduction of the Ground State Spin in Cr10 Wheel

“…This challenging goal has stimulated the research of chemically stable molecules that withstand surface‐deposition methods. The self‐assembly of monometallic molecules, such as phthalocyanines, [ 12,13 ] porphyrins [ 14 ] and bis(phthalocyaninato) lanthanide‐based complexes [ 15,16 ] is already well established, whereas there are only a few examples of polymetallic molecules robust enough to sustain a wide range of processes and experiments on surfaces, for example, {Fe 4 }, [ 17 ] {Mn 6 }, [ 18 ] and {Cr 7 Ni}. [ 19 ] Deposition by sublimation in ultrahigh vacuum (UHV) is the cleanest method to prepare molecular overlayers, something highly important for experiments that are sensitive to the molecule‐surface interaction.…”

Luminescent and Magnetic Tb-MOF Flakes Deposited on Silicon

“…The preparation of 2D molecular layers on surfaces is a prerequisite for the development of many applications. Different approaches have been utilized for this purpose, such as the self-assembly of evaporated molecules [ 31 ], the grafting of molecules on functionalized surfaces [ 32 , 33 ], and the use of surface-coordinated MOF thin films (SURMOFs) [ 34 ]. The use of hard-templates has also been proposed as an interesting strategy for engineering the structure of MOFs onto surfaces, as recently reviewed in [ 35 ].…”