Isolobal Solutions to the Hysteresis Challenge in Single-Molecule Magnetism

Magnetic materials containing rare-earth elements are indispensable to modern society, with their myriad applications ranging from the bulk scales of wind turbines and batteries for electronic vehicles to small-scale devices such as smart phones and computer hard-disk drives (HDDs). The use of rare earths in HDDs is particularly important since conventional technology for data processing relies on the unique magnetic properties of these elements to process and store digital information. This technology is struggling to keep pace with the rate at which data is generated and with the demands for processing it through increasingly sophisticated computer modelling processes.

To meet the demands of modern society and its thirst for generating extremely large amounts of data, there is a pressing need to develop new types of magnetic material capable of storing this data whilst simultaneously decreasing the physical size of the storage medium. In this project, we propose to develop solutions to the problem based on a simple premise: size matters.

The amount of data that can be stored in an HDD depends on the size of the magnetic particles; making these particles smaller should allow more digital information to be stored per unit area. Conventional rare-earth magnetic materials consist of particles with dimensions on the scale of tens of nanometres. In this project, we will synthesize a family of rare-earth magnets known as single-molecule magnets (SMMs), which store magnetic information at the level of individual molecules, typically with dimensions of less than one nanometre.

Molecules offer a major advantage over conventional atom-based magnets, which is that their properties can be improved rationally by changing the chemical environment in which the rare-earth elements reside. This facet allows us to address the major challenge in studies of SMMs, which is that their properties can only be observed upon cooling with cryogens, which is expensive and impractical.

In a ground-breaking development, the PI reported the first SMM to show magnetic memory effects above the boiling point of liquid nitrogen. The wider significance of this benchmark system is that it provides a blueprint for developing a new generation of high-temperature SMM. Therefore, in this project we will develop innovative chemical routes to a new generation of SMM with properties that can be observed at unprecedentedly high temperatures. Success with this project will potentially take an important step towards the incorporation of these materials into functional devices.

According to a recent report on bloomberg.com, the data market is predicted to be valued at $102.2 billion by 2024. Since data processing is relied upon by all types of business and public service providers in order to operate, the data market can only grow in the short, medium and long terms. However, the power of conventional computers is already starting to stretch the limits of what can be achieved by traditional manufacturing methods. Hence, in the future, sustainable solutions to impending data storage and processing problems will have to be based on alternative technology.

Data processing devices based on the quantum properties of atoms and molecules have tremendous potential to enable previously inconceivable advances in a range of settings, such as encryption/cryptography, data analytics and topological analysis, weather forecasting, medical research and traffic management based on autonomous vehicles. The data storage capabilities of single-molecule magnets have led to several prototype examples being developed as candidates for qubits, i.e. the basis of a quantum computer, hence such materials might be able to make considerable impact in this field of innovation.

In light of this, the most exciting findings from this research project have the potential to benefit a large range of stakeholders, including major players such as Volkswagen, Lockheed Martin and Airbus, who have already invested in quantum computers manufactured by D-Wave. Whilst the transition from funding basic research excellence to a marketable device will take time, an SMM with the right properties does respond to one of society's challenges and would allow the UK to develop a leading direction in this area of research and innovation. An indication of the importance of such an endeavour is highlighted by the investment made by IBM in fundamental research focusing on data storage at the level of single atoms, as described in Nature, 2017, 543, 226. This proposal has the same aims as the IBM work, but uses a different, chemical methodology that should allow us to go further in terms of the SMM performance parameters.

The primary aim of this proposal is to synthesize new SMMs that function at unprecedentedly high temperatures and to answer the question 'can room-temperature SMMs be made?'. In addressing these challenges, the PI draws a parallel with the grand challenge in superconductivity, where the race to make the first room-temperature superconductor has recently intensified with the discovery of material with a critical temperature of 250 K, albeit under a pressure of 170 GPa (see Nature 2019, 569, 528). Superconductors have been known for well over a hundred years, whereas the SMM field is still in its infancy. The fact that a room temperature superconductor has not yet been discovered is widely regarded as the justification for more research. Here; the PI argues the same case for SMMs. Whilst the challenges are substantial, the possible rewards for surmounting them are huge, not only from the perspective of fundamental research but also from the longer-term implications for computer devices based on the quantum properties of molecules.