The strongest magnetic materials available on the commercial market are based on the rare earth elements (Sc, Y, La–Lu) and the transition metals Fe and Co. In particular, neodymium iron boride (Nd-Fe-B) and samarium cobalt (Sm-Co) magnets had a transformative effect on technology in the latter half of the 20th century, enabling the miniaturisation of devices from earphones to hard disk drives. Today, these magnets have a similarly important role to play in the transformation to a low carbon, low emissions economy, being key components in wind turbines and in the drive motors of electric vehicles.
When constructing motors, it is essential that the magnetic components do not lose their magnetism even when heated up or exposed to other magnetic fields. Over the years, experimentalists have come up with ways to improve this "coercivity", e.g. by mixing other elements like dysprosium into the material. However, our theoretical understanding of coercivity is much more limited, not least because it involves physics on multiple length scales: from the quantum mechanics of electrons generating the magnetic order, to long range magnetic forces creating magnetic domains.
In this DPhil project we will aim to improve our understanding of coercivity in rare earth magnets through computational modelling. The primary focus of our modelling will be on the atomic scale, using "first-principles" density-functional theory calculations. However, a key part of the project will be linking the results of these calculations to other, larger-scale computational models of magnetic materials performed by collaborators, so that we can simulate the processes which determine the coercivity. A second key part will be comparing the model’s predictions with experimental measurements. The calculations will involve the use of supercomputers, and there will be opportunities to participate in code development. Therefore, this project would suit a student with a strong background in solid-state physics who is interested in learning about different approaches to modelling magnetic materials.