Magnetism of small transition metal clusters and the effects of isomerisation

TL;DR

This paper models the magnetic properties of small transition metal clusters considering isomer diversity, revealing complex magnetic behaviors influenced by multiple configurations and their energies, with implications for understanding experimental anomalies.

Contribution

It introduces a statistical model that accounts for isomeric diversity in predicting the magnetic properties of transition metal clusters, integrating ab initio data and Boltzmann weighting.

Findings

Isomers with similar energies can have vastly different magnetic properties.

The model explains some magnetic anomalies observed in experiments.

Magnetic susceptibility varies significantly with cluster isomer distributions.

Abstract

We investigate the magnetic properties of small transition metal clusters using a simple statistical model, which requires some input data from ab initio spin-density functional calculations. In our study we consider a thermodynamically equilibrated ensemble of clusters with different structures, spin multiplicities, and ground state energies. We calculate the physical properties of this system by weighting the individual configurations according to the Boltzmann statistics. We find that presence of isomers with very similar ground state energies, yet very different magnetic properties, gives rise to a rich magnetic behaviour of the system which differs significantly from what would be expected for single configurations. We apply the present model to to determine the magnetic susceptibility of a cluster ensemble of Langevin paramagnets. Our results show that some of the anomalies in the magnetic behaviour of transition metal clusters might be understood in the framework of our model which is, of course, limited by the extremely high computational effort needed to obtain the input data.