For convenience I have divided the projects below into those based on surveys of the literature (primarily for 3rd year MSci Physics Review Projects) and those based on experimental work or computation. However, it is often possible to devise projects based on these or my other research interests to suit your particular module and degree: please do come and discuss this possibility with me if you are interested.

Literature review projects

Multiferroic materials

Ferromagnetism, the behaviour of familiar magnets, has been known since prehistoric times: in fact, magnetic beads have been discovered in Sumerian tombs built six millenia ago. Since then, other ferroic behaviours have been discovered. For instance, just as a ferromagnet can ‘switch’ its magnetisation in response to an external magnetic field, a ferroelectric can switch its polarisation in response to an external electric field. Multiferroic materials combine two (or more) of these ferroic behaviours, and offer the possibility of coupling between them, so that, for instance, a material’s magnetic state could be altered by applying an electric field. Such materials find a wide range of technological applications.

This project will involve reviewing the theory behind multiferroicity, the multiferroic materials currently known, and the avenues currently being explored in the search for new materials. Depending on your interests, you could go on to investigate topics including the symmetry requirements for multiferroic behaviour; the differences between bulk, thin-film, heterostructure and nanostructure systems; or potential applications to technology.

One-dimensional magnetism

The behaviour of magnetic materials is radically different depending on in how many dimensions the magnetic sites are linked. Broadly speaking, the more “connected” the sites are, the more they will be influenced by sites far away from them. Thus if magnetic ions are joined into a 3D network, each influencing the behaviour of its neighbours, then they are likely to form a classical, magnetically ordered state. But if the magnetic sites form only a 1D chain, then there is far more scope for small regions to behave independently of one another, and the system’s behaviour will be dominated by quantum fluctuations. This project will involve reviewing the theory of this behaviour and the materials currently known to exhibit it. Depending on your interests, you could also consider quantum phase transitions more generally, or the experiments, particularly neutron scattering, used to investigate this behaviour.

Deuteration phase transitions

For most purposes the functional behaviour of materials is independent of the isotope of the atoms that make them up. In some cases, though, isotopic substitution can lead to remarkable differences. This project will focus on the changes associated with replacing hydrogen (¹H) by deuterium (²H). Doubling the nuclear mass suppresses quantum fluctuations and subtly alters the strength of hydrogen-bonding interactions, which affects the relative stability of different material phases. You will review the properties that it is possible to influence in this way and the applications of these effects to develop new functional materials.

Experimental and computational projects

Diffuse X-ray scattering from framework materials

Framework materials consist of metal ions linked together into a 3D network by organic molecules. To understand these materials' behaviour, we often need to consider not only their average structure, but also local deviations from that average. For instance, if a chain of atoms is sometimes buckled to the left, and sometimes to the right, the average gives a rather misleading picture of what is going on!

This project will involve measuring the diffuse X-ray scattering from a series of framework materials and running modelling software to analyse the resulting data. You will synthesise the materials, mount them as single crystals or powder samples on an appropriate diffractometer, and collect and analyse X-ray scattering data.

Polymorphism in framework materials

Many complex materials exhibit polymorphism, the property whereby the same component atoms and molecules can form multiple different crystal structures. These structures will often have remarkably different physical properties, and hence it is important to understand and be able to control these variations.

This project will involve running ab initio computer simulations – that is, simulations based entirely on calculation, rather than using experimental data – in order to search for polymorphs of functional framework materials and compare their stability. We will also compare our results to experimental data where available.

For this project some familiarity with Linux/Unix systems would be useful.

Cation dynamics in electrically active materials

Materials with high dielectric constant are useful in a variety of electronics applications, including to store energy in capacitors. One family of such materials owes its high dielectric constant to the movement of organic cations within “cages” in the framework structure. These cations are able to rotate in response to an external field, “screening” it.

Depending on your interests, this project will either involve analysing experimental neutron scattering data from these materials, modelling them with computer simulations, or both. In each case the aim will be to understand the cation motion and how it is controlled by cation-framework interactions, with the ultimate goal of using this understanding to design new dielectric materials.