Atomic Clusters Mimic Rare Earth Magnetic Properties

A team of scientists from the United States recently created boron-doped atomic clusters that exhibited electronic and magnetic properties of valuable rare earth metals and hence can potentially serve as rare earth substitutes in the future.

Rare earth metals get their namesake from the fact that they invariably exist in extremely low concentrations where they are found, often only as trace impurities in ores of other metals. This makes rare earth extraction technically difficult, financially costly, and very polluting to the environment. These metals are indispensable in modern society as raw materials to many technological products due to their unique electronic and magnetic properties. As such, there is a real imperative for the development of viable rare earth substitutes.

Albert Castleman’s team at the Pennsylvania State University used laser ablation to vaporize lanthanum (La) and neodymium (Nd) in an inert helium atmosphere containing gaseous diborane (B₂H₆) to create the boron-doped clusters LaB and NdB.

To investigate the properties of the clusters, the team used a technique known as photoelectron spectroscopy, which ejects electrons from the samples using ultraviolet light and measures the characteristic energies from the process. The team found the electronic structure of LaB as identical to that of elemental Nd, and that of NdB as identical to that of europium (Eu), another rare earth element. Given that raw Eu and Nd cost more than ten times as much as Nd and La respectively, this work is in principle a significant step up the value chain.

Of course, this does not mean that the new materials are ready to replace the expensive rare earth metals just yet – for one, laser ablation is not a practical method to produce bulk material, and on top of that the properties of a compound in gaseous cluster form is not entirely reflective of how it will behave as a bulk solid.