Magnetic subunits within a single molecule–surface hybrid

Abstract

Magnetic molecule-surface hybrids are ideal building blocks for molecular spintronic devices due to their appealing tailorable magnetic properties and nanoscale size. So far, assemblies of interacting molecular-surface hybrids needed for spintronic functionality were generated by depositing aromatic molecules onto transition-metal surfaces, resulting in a random arrangement of hybrid magnets due to the inherent and strong hybridization. Here, we demonstrate the formation of multiple intramolecular subunits within a single molecule-surface hybrid by means of spin-polarized scanning tunneling microscopy experiments and ab initio density functional theory calculations. This novel effect is realized by depositing a polycyclic aromatic molecule on a magnetic surface. A highly asymmetric chiral adsorption position induces different structural, electronic, and magnetic properties in each aromatic ring of the molecule. In particular, the induced molecular spin polarization near the Fermi energy varies among the rings due to site-and spin-dependent molecule-surface hybridization. Our results showcase a possible organic chemistry route of tailoring geometrically welldefined assemblies of magnetically distinguishable subunits in molecule-surface hybrids.

Quantum interference effects in molecular spin hybrids

“…An inversion of the spin polarization of the hybrid state in comparison to the d-like surface state is reasonable, since we deduced in section III C that the TPT molecules must be strongly hybridized with the Co islands, and a strong hybridization results in a inversion of the spin polarization in agreement with previous combined STM and DFT studies 27,31,32 and model calculations 20 .…”

“…The spin-sensitive measurements revealed that the spin polarization varies among the different aromatic rings of the TPT molecule, although the molecules exhibit a highly symmetric adsorption geometry as revealed by atomically resolved STM images and confirmed by ab initio calculations that yield the highest binding energy for the experimentally ascertained adsorption site. Hence, the varying degree of spin polarization on the different aromatic rings cannot stem from a different hybridization of the aromatic rings with the ferromagnetic substrate as recently observed for TPT on Fe/W(110) 27 . Given that the spatially resolved spin asymmetry maps also showed a modulation of the spin polarization on the uncovered parts of the Co islands, we propose to link the appearance of the intramolecular variations of the spin polarization to a superposition of the spin polarization of the TPT molecule and the spatially modulated spin-polarized sp surface state of the Co(111) surface.…”

“…Significant intramolecular variations of the electronic and magnetic properties among the aromatic rings have recently been observed for TPT molecules adsorbed on 2 ML Fe on W(110) 27 . In this case the combination of the 3-fold symmetric TPT molecule and the 2-fold symmetric substrate lattice leads to a highly asymmetric and chiral adsorption geometry with different bonding and hybridization conditions for the three peripheral phenyl groups in each TPT molecule.…”

“…Such effects can lead to magnetic hardening or softening of the newly formed unit consisting of the chemisorbed molecule and its direct metal neighbors 19,23,24 . Since such new hybrid systems promise unique magnetic functionalities, they are currently studied intensively 19,21,[25][26][27][28][29][30] .…”

Hot Electrons and Hot Spins at Metal–Organic Interfaces

“…The distance between the metallic surface and the first organic layer () may be smaller than a . It depends on the specific molecule and its interaction with the surface and could be determined by experimental techniques or ab initio calculations. Here we will use a density functional theory based distance from energy relaxation calculations .…”