High density data storage with rare earth molecules
A joint University of Melbourne-ANSTO team has used neutron scattering and theoretical modelling to advance the development of rare earth molecules for high density magnetic data storage.
Our modern digital society generates an ever-increasing amount of electronic data every day. Current technology uses ensembles of magnetic nanoparticles to store data locally in magnetic films in computer hard drives or in “the cloud” in global data centres as magnetic tape. The nanoparticles of iron oxide or cobalt alloys that comprise the magnetic storage units in films or tape store the data as a series of binary ones and zeroes. Efforts to increase storage density have relied on miniaturisation of the storage units by decreasing the magnetic nanoparticle size. However, the ability to further decrease the size of these nanoparticles is rapidly approaching the so-called “superparamagnetic” physical limit, which inhibits efforts to increase magnetic data storage density and therefore capacity.
Single-molecule magnets (SMMs) are compounds that can retain magnetisation at the level of individual molecules. They represent the ultimate limit of miniaturisation of magnetic units for high-density data storage, offering a potential hundred to a thousand-fold improvement in capacity over conventional nanoparticles. They also have potential applications in quantum computing and molecular spintronics. The best-performing SMMs are based on rare earth metals with magnetic properties that can be enhanced by coupling to radical organic ligands. However, determining the electronic structure of these coupled units is challenging but essential to inform the design of improved SMMs for applications.
An ARC-funded joint University of Melbourne-ANSTO research study, led by Colette Boskovic, Alessandro Soncini and Richard Mole, has advanced this pursuit by combining a suite of experimental techniques and state-of-the-art computational methodology to investigate rare-earth-radical SMMs. The experimental work for this study was mainly carried out by Maja Dunstan as part of her PhD. This included extensive neutron scattering studies undertaken at the Australian Centre for Neutron Scattering using neutrons generated by the Open-pool Australian Lightwater (OPAL) nuclear reactor at Lucas Heights. The experimental findings were complemented by ab initio calculations from Marcus Giansiracusa. This investigation has revealed the highly entangled nature of the 4f-radical exchange states, providing spatial information of the wave function as visualised by neutron scattering spectroscopy.
This work represents a significant advance for the determination of electronic structure in molecules with coupled rare earth spin carriers, which are of critical importance for developing high performance molecular magnetic materials for high density data storage.