Spin transfer and distance-dependent spin coupling in linearly assembled Ag-Cu nanoclusters

The magnetism performance of Ag₇₇Cu₂₂ nanoclusters after assembly and disassembly (The inset in the red circle shows the absence of spin coupling in Au₂₅⁰ due to the long interparticle distance. 1 credit

In a recent study published in Nature Communicationa research team led by Professor Wu Zhikun of the Hefei Institutes of Physical Sciences (HFIPS) of the Chinese Academy of Sciences discovered spin transfer and spin coupling by the linear assembly of silver-copper alloy nanoclusters (Ag-Cu) with sulfur.

The assembly of metallic nanoparticles not only enriches their properties, but also helps to understand structure-property relationships and interactions between nanoparticles. However, due to the multi-distribution of metallic nanocrystals, it is difficult to obtain atomically precise assembly structures.

Recently emerged nanoclusters (ultra-small nanoparticles) provide ideal building blocks for precise assembly due to their well-defined compositions and structures; however, few studies on the assembly of atomically precise metal nanoclusters (more than 1 nm) have been reported due to the difficulty of synthesis and characterization.

In this study, the team prepared a linear assembly structure formed by connecting two Ag₇₇Cu₂₂ clusters with a sulfur ion using a simultaneous synthesis and assembly strategy. Sulfur ions can be produced by the cleavage of carbon-sulfur and sulfur-hydrogen bonds of thiols during cluster synthesis, leading to immediate bonding with the clusters to form the assemblies.

Further studies showed that the magnetic moment in this linear assembled structure was transferred from the cluster to sulfur, forming paramagnetic sulfur radicals, which exhibited magnetic isotropy due to the small spin-orbit coupling constants of sulfur and the absence of interaction of the magnetic moment between sulfur radicals.

When the linear structures were disassembled in solution, the magnetic moment was transferred back to the clusters, and subsequently spin coupling occurred. Notably, such spin coupling had not been reported in magnetic Au₂₅⁰ clusters, which was interpreted by interparticle distance-dependent spin coupling.

And when the ligands were flexible and their lengths were short, the clusters could get closer and the spin coupling occurred at a certain distance. Otherwise, it was difficult for the clusters to get closer for coupling.

This work achieves the linear assembly of metal nanoclusters larger than 1 nm using the appropriate assembly strategy. He discovers and explains spin transfer and distance-dependent spin coupling, which could have important implications for the future study of nanocluster magnetism and the development of new functional materials.