Spin Excitations of High Spin Iron(II) in Metal-Organic Chains on Metal and Superconductor

TL;DR

This study investigates the spin excitations of high-spin Fe(II) in metal-organic chains on different substrates, revealing substrate-dependent variations in spin-spin interactions influenced by electronic states.

Contribution

It demonstrates how substrate electronic properties affect spin interactions in metal-organic chains, using advanced microscopy and synthesis techniques.

Findings

Spin-spin coupling observed on Ag(111) is absent on Pb(111).

Electronic state depletion in Pb(111) reduces spin interactions.

High-spin Fe(II) chains can be synthesized on different substrates.

Abstract

Many-body interactions in metal-organic frameworks are fundamental for emergent quantum physics. Unlike their solution counterpart, magnetization at surfaces in low-dimensional analogues is strongly influenced by magnetic anisotropy induced by the substrate and still not well understood. Here, we use on-surface coordination chemistry to synthesize on Ag(111) and superconducting Pb(111) an iron-based spin chain by using pyrene-4,5,9,10-tetraone precursors as ligands. Using low-temperature scanning probe microscopy, we compare their structures and low-energy spin excitations of coordinated Fe atoms with high S = 2 spin-state. Although the chain and coordination centers are identical on both substrates, the long-range spin-spin coupling due to a superexchange through the ligand observed on Ag is absent on Pb(111). We ascribe this reduction of spin-spin interactions on Pb to the depletion of electronic states around the Fermi level in the Pb(111) superconductor as compared to silver.