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

Abstract

We report the deposition of monolayers and multilayers of {Cr 10 (OMe) 20 (O 2 CCMe 3 ) 10 } wheels, hereafter {Cr 10 }, onto Au(111) and Cu(111) single-crystal substrates, and their characterization combining scanning tunneling microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, X-ray natural linear dichroism, and X-ray magnetic circular dichroism (XMCD). {Cr 10 } in bulk shows axial magnetic anisotropy and a cluster total spin S = 9 ground state, stemming from an interaction scheme of two semi-crowns containing four Cr 3+ ions interacting ferromagnetically, separated by two Cr 3+ antiferromagnetically coupled. The one-monolayer (1ML) samples of {Cr 10 } sublimated on Ag(111) and Cu(111) show slightly different applied magnetic field dependence of XMCD signal. The field-dependence of the magnetization evolves from a lower curve for the 1ML {Cr 10 } samples to a curve resembling the bulk one as the number of layers is increased, as shown in a 14ML sample. Monte Carlo simulations allow rationalizing the magnetization curves of the 1ML samples in terms of a reduction of the cluster ground-state total spin, S = 3 or S = 6, as a consequence of variations in the intra-wheel coupling interactions induced by the on-surface deposition. The sensitivity of the magnetic configuration of {Cr 10 } to minor distortions of the intramolecular conformation might be exploited to control magnetism by external stimuli for applications.