Spin-Flip Inelastic Electron Tunneling Spectroscopy on a CuCu4 Metallacrown Complex on Au(111)

Abstract

Spin-flip inelastic tunneling spectroscopy (SF-IETS) is an outstanding technique to investigate elementary spin excitation of adsorbed atoms, molecules, and their assemblies on surfaces. The analysis of the measured spectra provides access to the spin interactions within adsorbed spin systems and their coupling with the substrate electrons. Here, we use SF-IETS in combination with different perturbative electron transport model simulations to explore the spin excitation processes in the Cu­(II)­[12-MCCu(II)N(Shi)-4] metallacrown molecule (CuCu4), containing five half-spin centers, after adsorption on an Au(111) surface. In contrast to published SF-IETS spectra of other multispin-carrying systems decoupled from the metal surface, showing a step-like function, the signatures of the CuCu4/Au(111) systems differ significantly. These spin-flip signatures could be reproduced by considering spin–spin exchange scattering with the substrate electron bath using an up to 3rd-order perturbative electron transport model in the simulations. The results give access to the system’s superexchange coupling constants with the resulting spin ground state and lead to a better understanding of the spin dynamics of such multiple spin-bearing molecules. Our results do not only give insight into a system that may be utilized in molecular spintronics but may open a route to manipulate spins in nonmagnetic metals on a nanometer scale.