Orchestration of Ferro- and Anti-ferromagnetic Orders in Gold Nanoclusters

Abstract

The unpaired electron in the gold clusters (Au_n, n = no. of Au atom) with odd number of total electrons is solely responsible for the magnetic properties in the small-sized Au nano-clusters. However, no such unpaired electron is available due to paring in the even number of atom gold clusters and behaving as a diamagnetic entity similar to the bulk gold. In this work, we unveiled the spin-density distribution of the odd Au_n clusters with n=1 to 19 that reveals a single unpaired electron gets distributed non-uniformly among all Au-atoms depending on the cluster size and morphologies. The delocalization of the unpaired electron leads to the spin dilution approaching a value of ∼ 1/n spin moments on each atom for the higher clusters. Interestingly, small odd-numbered gold clusters possess spin-magnetic moments similar to the delocalized spin moments as of organic radicals. Can cooperative magnetic properties be obtained by coupling these individual magnetic gold nanoparticles? In this work, applying state-of-the-art computational methodologies, we have demonstrated ferromagnetic or anti-ferromagnetic couplings between such magnetic nanoclusters upon designing suitable organic spacers. These findings will open up a new avenue of nanoscale magnetic materials combining organic spacers and odd-electron nano-clusters.