Materials and Condensed Matter Physics

Challenges facing technology for power efficient, high density, high speed information processing and storage are well recognised, and strategies for meeting them in the short term define the shape of industry roadmaps. As a consequence, in the next ten years, radically new approaches will be implemented and will transform how data is stored and manipulated. Skyrmion-based devices are newcomers to this global race for the next generations of information technology. Skyrmions were discovered in magnetic crystals only a few years ago, but we already have within reach a possibility to create them in nanoscale devices that can be made compatible with conventional integrated circuit technology. Our work in MAGicSky will substantiate this possibility.
The potential benefits are enormous. Skyrmions are magnetic solitons that carry information, and are remarkably robust against defects that can trap or destroy them due to the topology of their magnetic texture. Topology also appears to further underlie other of their technologically important features: mobility with small continuous currents and singular dynamics under radio-frequency. MAGicSky will engage some of the most advanced materials fabrication, characterisation and microscopic imaging facilities in Europe together with leading theoretical and computational modelling capabilities, to create the first proof-of-concept room temperature spintronic devices based on magnetic skyrmions.

Thermoelectric materials convert waste heat into useful electric power. Even inefficient thermoelectric power generation recovery can have a substantial impact on UK and global energy consumption because more than half of primary energy is ultimately wasted as heat. So far, thermoelectric generators (TEGs) have been restricted to niche applications, such as powering the Voyager space probes, where durable, reliable and low-maintenance power generation is essential. However, the market for thermoelectric energy harvesters is projected to approach $1bn within a decade.* Potential applications for TEGs include scavenging heat from car exhausts, producing combined heat and power units for use in remote, off-grid locations, and replacing batteries in wearable microelectronic devices. A major limitation has been to develop cheap, efficient TEGs that do not rely on toxic or scarce resources. For example, the most efficient thermoelectric material for automobile heat recovery is currently a compound of toxic lead and scarce tellurium.
In this project, we aim to develop a viable, non-toxic alternative to lead telluride TEGs, using 'Heusler alloys', which combine abundant elements such as titanium, nickel and tin. They also meet the majority of industrial requirements for thermoelectric power generation, having good thermal and mechanical stability, mechanical strength and ease of processing. However, a TEG's thermal conductivity is also critical and optimising the thermal conductivity of Heusler alloys has been problematic. We aim to capitalise on our recent advances in Heusler alloy synthesis and nanostructuring, which currently represents the only UK efforts in this fast-growing field.
The ultimate aim of this proposal is to develop new means of controlling the thermal conductivity of Heusler alloys in order to build a TEG prototype of comparable performance to existing lead telluride devices. Our insight is that there are a variety of alloy phases and intentional defects that can be used to introduce structural texture on the nanoscale, thereby reducing the thermal conductivity. What is exciting is that many of these structures have not previously been studied. A critical aspect is the size and distribution of the texturing, which should be long enough to avoid reducing the material's electrical conductivity but short enough to impede the flow of heat. We will investigate the optimum length-scales for texturing by performing a systematic study of the impact of processing conditions on the HA nanoscale structure. We will use worldleading electron microscopy, neutron scattering facilities and theoretical modelling to probe the atomic-scale structure and dynamics of the new materials in order to optimise the synthesis parameters. We will then use this technical know-how in collaboration with our industrial partner European Thermodynamics Ltd. to build prototype TEG modules.
This collaborative project, involving three academic institutions, national facilities and a UK small business, has substantial potential for impact, with notable prospects for making a contribution to lowering the UK's carbon footprint. It also provides excellent opportunities for knowledge transfer to a vibrant new industry and for high-quality training.
* H. Zervos, "Thermoelectric Energy Harvesting 2014-2024: Devices, Applications, Opportunities," 2014

Current-driven domain wall motion and magnetomemristance in FeRh-based nanostructures
(Full abstract not yet available.)

Our project is a collaborative one between two Universities and a national laboratory working together across a combined theoretical and experimental programme. The experiments are based in both conventional laboratories and large-scale facilities. The work programme also involves continued international collaboration with colleagues in the US at Brookhaven National Laboratory, who have helped us make some of our most recent breakthroughs in creating and understanding nanostructured magnets, as well as adding new ones in the form of the unique expertise and facilities available for transmission x-ray imaging at the Advanced Light Source in Berkeley. Both of these are DOE-supported US national laboratories.

Chirality is ubiquitous and underpins our understanding of research fields as diverse as particle physics and molecular biology. It is the symmetry property of an object to exist as distinguishable left- and right-handed forms. Chirality also governs useful electronic and optical properties of many advanced materials. We will now use our understanding of this electronic and structural chirality to create a variety of new technologies. We will establish an international consortium centred on the exploitation of electronic chirality in advanced materials, with a particular interest in their electromagnetic response. We will combine international expertise spanning the synthesis, characterisation and theory of chiral electronic media with an ambition to make advances in a variety of technologies, ranging from next generation information and communication technologies to improved bio-sensors. Our consortium comprises 4 core scientists and additional collaborators from across the University of Glasgow and 18 core scientists from Universities and Institutes in Tokyo, Osaka, Kyushu and Hiroshima. It will be augmented by collaboration with Ural Federal University, Russia and Monash University, Australia. It will be facilitated by a number of meetings, research visits, researcher exchanges and larger conferences involving the broader community.

We target three broad themes, in which our individual expertise will be stimulated by fresh perspectives brought by the consortium.

1) Atomic-scale electronic chirality and novel magnetic crystals.
A simple manifestation of electronic chirality is the emergence of magnetism. The most fundamental electronic correlations in chiral crystals can give rise to a variety of magnetic orderings, of which only a small subset (skyrmions) have been recognised as potentially useful. Our insight is to study the largely overlooked area of helicoidal media, which have spiral arrangements of magnetic moments and are more robust and easier to realise than skyrmions. We will combine our expertise in chiral materials (Hiroshima) with internationally-leading electron microscopy of magnetic materials (Glasgow) and theory (Urals) to propel an exploration of artificially designed and naturally occurring helicoidal magnetic materials that have strong potential for applications utilising magnetoresistance and magneto-optical response.

2) Micron-scale electronic chirality and chiral plasmonic metamaterials.
Plasmons - collective electronic excitations - can interact strongly with electromagnetic radiation, particularly in patterned metallic structures. We will explore chirally patterned media that we have already demonstrated to have a number of applications. For example, Glasgow has pioneered the use of such chiral plasmons as ultra-sensitive sensors for chiral biomolecules whilst Tokyo has expertise in the optical characterisation of such structures. A second application is the development of on-chip plasmonics to form the basis of a wide class of devices suitable for THz applications (Glasgow), which we will now augment by incorporating chiral patterned magnetic materials as reconfigurable components. These composite structures offer new possibilities for application as THz phase shifters or sensors for functionalised nanoparticles.

3) Chirally-sensitive electron probes.
The study of chiral materials is eased by the development of chiral-specific techniques. Glasgow has long-standing expertise in the use of chiral photon probes in the context of optical orbital angular momentum for light beams whilst Monash has expertise in forming analogous electronic probes that would be suitable for chirally-specific electron microscopy. Prototypical measurements in the use of such vortex beams for imaging plasmonic structures and chiral spin textures are already underway (Hiroshima, Glasgow) and will be employed for the first time in the study of materials generated in both of the above themes.

The research proposed here aims to develop entirely new ways of imaging in the electron microscope, and to use these methods to study real-world materials problems. To illustrate the power of the methods we propose to develop, we have selected proof-of-principle materials problems from the areas of carbon nanotechnology, life sciences and electronic device structures.

Over the past couple of decades a particular type of electron microscope, the scanning transmission electron microscope (STEM) has become increasingly popular due to its high-spatial and energy-resolution. Much of our understanding of how macroscopic materials properties relate to atomic structure and bonding, and how we can control properties by manipulating these, is a result of the development of techniques to characterise materials on very short length scales. The STEM is not only capable of imaging atoms and observing the structure and crystallographic details of materials, but also in performing spectroscopy on single atoms, allowing atom-by-atom chemistry to be determined. A further key development is the spherical aberration corrector, which has revolutionised the performance of these instruments by overcoming the earlier limitations of electron lenses.

The principle of STEM is the use of electron lenses to focus a beam of electrons to form a small illuminating spot or probe. The probe can be scanned across a sample using a beam deflector. A thin, electron-transparent sample is used, and transmitted electrons can be detector, and the intensity of those detected plotted as a function of the probe position during a two-dimensional scan to form an image. The mostly commonly used detectors are an annular dark-field (ADF) detector which is a detector in the form of a broad annulus that detects relatively high angles of scatter, and bright-field (BF) detectors that collect the unscattered and low-angle scattered electrons. Both these detectors collect the total scattering over a range of scattering angles, and the total intensity is used to form an image. Such an approach neglects the rich information that is contained in the fluctuation in intensity that occurs as a function of scattering angle.

The overarching aim that forms the basis of the current proposal is to use fast pixelated detectors to record the intensity as a function of scattering angle in the detector plane of a STEM, which is effectively a diffraction pattern. By recording each two-dimensional diffraction pattern as a function of probe position in a two-dimensional scan, a four-dimensional data set can be recorded that is the ultimate STEM imaging experiment. Such a rich dataset contains information about the phase shift that results from transmission, about the composition of the sample, the strain in the sample and the three-dimensional ordering in the sample. We propose to develop the methods to record this 4D data set, using fast pixelated detectors, and by developing an optimised direct-detection system, together with the methods to process such datasets to enable physically useful measurements to be made.

We believe the approach we are taking will create a paradigm shift in STEM imaging, and in time will become the standard approach to record data in the STEM. To illustrate the power of the approach, we have identified key materials science questions that we will address with the methods we develop. The applications are: (i) imaging charge transfer in doped nanomaterials; (ii) imaging of soft and radiation sensitive materials, (iii) imaging of electric and magnetic fields in magnetic nanostructures, (iv) 3D composition and structural ordering effects in ceramics; (v) interdiffusion in ceramic and semiconductor heterointerfaces.

The methods developed will be disseminated widely, particularly through their implementation at the EPSRC National Facility for Aberration-Corrected STEM (SuperSTEM) through which a wide range of users will be able to access the new methods.

Information technology and the Internet are central to our society and these technologies require storage of digital information on an exponentially increasing scale. There are two principal types of storage: traditional hard disk drives (HDD) that provide high density storage at low cost, and solid state drives (SSD) that offer less capacity at greater price, but are more power efficient and have no mechanical parts. While most personal computing and related electronic devices are migrating to SSD the need for HDD is also increasing - in a local context (e.g. personal TV and video recorders) and also remotely, particularly in cloud computing. Cloud computing is a rapidly growing sector, where already almost all of e-commerce and the internet and much of the engineering industry rely on data farms filled with large numbers of 'server' computers using HDD to store information. These data range from personal information such as bank details and social media through to environmental data, data related to health and company and institution specific data. Cloud computing accounted for 25% of storage use in 2010 and by 2020 it will account for >60% - a server is required for every 600 smartphones or 120 tablet computers. As a result, HDDs of ever increasing capacity are required.

Due to the limitations of current materials, a new technology will be needed to increase the density of magnetic data recording at the present rate, and it envisaged this technology will be heat-assisted magnetic recording (HAMR). HAMR will require the integration of photonic components such as lasers, waveguides and plasmonic antennas within a magnetic recording head.

HAMR will only be successful if it can be deployed as a low-cost manufacturable technology. Its successful development will therefore drive low-cost photonic integration and plasmonic technology into other industries and applications. The CDT will address the challenge with a critical mass of partners from universities and industry to meet this challenge and undertake the training of successive cohorts of research students in a set of cognate technical topics:

• Ultra-reliable semiconductor lasers operating in hostile environments (the laser may have to operate at temperatures of 100 degree C)
• Low cost planar lightwave circuit (PLC) platforms and laser and antenna coupling schemes, suitable for volume manufacture
• Novel nanoplasmonic antennas capable of operating in extreme environments (200-300 degree C and pressures up to 10 atm. at the disk/head interface)
• Advanced materials for magnetic recording
• Atomic scale analysis techniques

This suite of technologies must be highly manufacturable and suitable for heterogeneous integration in a rugged platform. The successful development of HAMR technology will see a paradigm shift in the performance of data storage devices but the low-cost ruggedized heterogeneous integration technology will also be applicable in multiple markets. Although the HAMR environment is particularly harsh, many other consumer and society driven applications (such as widely deployable high speed internet) also require operation in harsh environments.

Our industry partners have identified that distributed working is an element missing from existing doctoral training. Much R&D in cutting edge technology is undertaken collaboratively across geographically separated sites because of the need to thread together expertise and capability that is often not co-located. It is important that doctoral students gain experience in this way of working and develop the skills and strategies to become adept and effective in this environment.

The technical capability required to address the range of photonic and heterogeneous integration requirements for advanced data storage does not reside within one single University in the UK and therefore collaboration across the partner university sites provides the vehicle for delivering training in distributed working.

The aim of this project is to develop a detailed physical understanding of the thermodynamic and kinetic behaviour of precipitation in high manganese austenitic steels and to provide essential data for the modelling of technologically important (iron-carbide and transition-metal-carbide) precipitation processes in this new generation of high strength alloys. No equivalent data is to be found anywhere in the existing literature. New precipitation models will be validated and published in a form which can easily be integrated with existing codes.

Ion beam preparation and the ability to use it for precision lithography has made it one of the most interesting and useful tools in materials science. It is key to the preparation of high quality site-specific specimens for transmission electron microscopy and scanning transmission electron microscopy and its versatility as a nanoscale scalpel makes it an essential tool for nanostructuring shapes and designs that are often difficult or impossible to realise otherwise. Building upon our long track record in focused ion beam preparation and expertise in materials characterisation we will commission a 3rd generation focused ion beam instrument. This design replaces the gallium beam used in the 1st and 2nd generation instruments with a noble gas beam for milling. The use of noble gas beams has major advantages over gallium in reducing chemical reactions, implantation and surface damage. In consequence we will be able to extract the greatest possible information from advanced high-resolution electron microscopy by reducing artefacts and ambiguities when preparing cross sections and lift outs. Moreover, with the 3rd generation machine our ability to define features lithographically will benefit from a significant improvement in definition. This will allow us to create and study functional nanostructures in a greater range of material systems than currently possible. The addition of this state of the art tool to the Kelvin Nanocharacterisation Centre at Glasgow will add value to numerous projects and collaborations at the University of Glasgow, across Scotland and throughout the north of the UK, a noble gas FIB that is optimised for the liftout of high quality TEM/STEM specimens will be of especial national importance as the first instrument of its kind funded by the EPSRC anywhere in the UK. Access mechanisms will be put in place to allow users from across the UK to use this facility, as detailed elsewhere. We will track the significant industrial impact this instrument will have, including with existing industrial partners on advanced materials development, as well as in collaboration with the instrument suppliers to further develop usage modes and protocols with a clear benefit to future users of such technology. This will also benefit the training of a future generation of scientists and technologists through its explicit linkage to two Centres for Doctoral Training.

The research proposed here aims to develop entirely new ways of imaging in the electron microscope, and to use these methods to study real-world materials problems. To illustrate the power of the methods we propose to develop, we have selected proof-of-principle materials problems from the areas of carbon nanotechnology, life sciences and electronic device structures.

Over the past couple of decades a particular type of electron microscope, the scanning transmission electron microscope (STEM) has become increasingly popular due to its high-spatial and energy-resolution. Much of our understanding of how macroscopic materials properties relate to atomic structure and bonding, and how we can control properties by manipulating these, is a result of the development of techniques to characterise materials on very short length scales. The STEM is not only capable of imaging atoms and observing the structure and crystallographic details of materials, but also in performing spectroscopy on single atoms, allowing atom-by-atom chemistry to be determined. A further key development is the spherical aberration corrector, which has revolutionised the performance of these instruments by overcoming the earlier limitations of electron lenses.

The principle of STEM is the use of electron lenses to focus a beam of electrons to form a small illuminating spot or probe. The probe can be scanned across a sample using a beam deflector. A thin, electron-transparent sample is used, and transmitted electrons can be detector, and the intensity of those detected plotted as a function of the probe position during a two-dimensional scan to form an image. The mostly commonly used detectors are an annular dark-field (ADF) detector which is a detector in the form of a broad annulus that detects relatively high angles of scatter, and bright-field (BF) detectors that collect the unscattered and low-angle scattered electrons. Both these detectors collect the total scattering over a range of scattering angles, and the total intensity is used to form an image. Such an approach neglects the rich information that is contained in the fluctuation in intensity that occurs as a function of scattering angle.

The overarching aim that forms the basis of the current proposal is to use fast pixelated detectors to record the intensity as a function of scattering angle in the detector plane of a STEM, which is effectively a diffraction pattern. By recording each two-dimensional diffraction pattern as a function of probe position in a two-dimensional scan, a four-dimensional data set can be recorded that is the ultimate STEM imaging experiment. Such a rich dataset contains information about the phase shift that results from transmission, about the composition of the sample, the strain in the sample and the three-dimensional ordering in the sample. We propose to develop the methods to record this 4D data set, using fast pixelated detectors, and by developing an optimised direct-detection system, together with the methods to process such datasets to enable physically useful measurements to be made.

We believe the approach we are taking will create a paradigm shift in STEM imaging, and in time will become the standard approach to record data in the STEM. To illustrate the power of the approach, we have identified key materials science questions that we will address with the methods we develop. The applications are: (i) imaging charge transfer in doped nanomaterials; (ii) imaging of soft and radiation sensitive materials, (iii) imaging of electric and magnetic fields in magnetic nanostructures, (iv) 3D composition and structural ordering effects in ceramics; (v) interdiffusion in ceramic and semiconductor heterointerfaces.

The methods developed will be disseminated widely, particularly through their implementation at the EPSRC National Facility for Aberration-Corrected STEM (SuperSTEM) through which a wide range of users will be able to access the new methods.

Our project is a collaborative one between two Universities and a national laboratory working together across a combined theoretical and experimental programme. The experiments are based in both conventional laboratories and large-scale facilities. The work programme also involves continued international collaboration with colleagues in the US at Brookhaven National Laboratory, who have helped us make some of our most recent breakthroughs in creating and understanding nanostructured magnets, as well as adding new ones in the form of the unique expertise and facilities available for transmission x-ray imaging at the Advanced Light Source in Berkeley. Both of these are DOE-supported US national laboratories.

Our goal is to understand and control non-equilibrium dynamics in a new class of magnetic materials: strongly correlated arrays of sub-micron sized magnets. Examples have been studied recently, and given the name "artificial spin ice". These materials are important examples of new metamaterials with unique properties not realised in naturally occurring magnetic materials. The artificial magnetic ice are systems composed of strongly interacting magnetic moments, and the moments are arranged geometrically in order to produce metastable configurations with a high degree of degeneracy in energy. We will use artificial spin ice as a paradigm for a systematic exploration of non-equilibrium dynamics. This is a model system for which the free energy is specified by design and hence completely determined, and the exact microstate--and its evolution in time--can be observed directly for detailed comparison with mathematical predictions.

Inter-element interactions can be specified to a large extent by design through control of geometry. In this way it is possible to create competitions between ordering that result in geometrical frustrations responsible for complex response to applied magnetic fields. The resulting magnetic properties are analogous to those of traditional thin film or bulk magnetic systems, but with key differences that can be of especial importance for applications. For example, there are two ground state configurations in a square ice that form domains with zero net moment. These are separated by magnetised boundary walls along which magnetic charges can move.

Respiratory syncytial virus (RSV) infects very young babies and children causing severe respiratory disease that often requires hospitalisation and is sometimes fatal. RSV also infects the elderly and people with weak immune systems. Scientists have not yet been able to invent vaccines or medicines for this virus. It is very important then to build our understanding of this dangerous disease to find new ways of attacking the virus. This project aims to achieve this by using a very powerful electron microscope to look, in three dimensions (3D), at the shape of the virus and the different protein molecules it is made from. We have started this work by growing cells on a special support that allows us to put them into the microscope. These cells can be infected with RSV, which reproduces inside them. New virus particles grow out of the cells as long filaments. We can freeze the infected cells very quickly, to preserve their structure, and then examine them at very high magnification in the microscope. We then use computers to process images recorded in the microscope to build 3D maps of the virus that help us understand the shape of the molecules it is made from. By understanding how these different molecules stick together we hope that researchers will be able to invent new medicines that will interfere with the virus and stop it reproducing.

In this study we will focus on two key elements of the virus. Firstly we will look at a protein molecule called the matrix protein, or M. This protein directs the assembly of the virus by binding to the internal viral components and bringing them to the cell surface where the virus forms. M also binds to special viral proteins called F and G that are found on the outer-surface of the virus. These proteins are important for the newly formed virus particles to be able to infect new cells. Thus M is the coordinator of virus assembly and its interactions with other viral proteins are key targets for researchers looking to prevent the spread of infection.The internal components of the virus include a structure known as the nucleocapsid, which contains the virus's genetic code. Bound to this is another structure called the 'polymerase' a protein that copies the genetic code so that more virus particles can be made. This assembly is the second component of RSV that we are interested in solving the structure of. We may be able to achieve this by looking for the polymerase bound onto the nucleocapsid in the virus itself. Another approach is to make the structure artificially in the laboratory. This has proven very difficult but co-investigator Dr Rachel Fearns of Boston University has managed to achieve this recently. Together we will purify large quantities of the polymerase which we can examine in the electron microscope to determine its structure. The higher resolution we can achieve by this approach should provide us with a more detailed understanding of how the polymerase works. The final component of this project will be to develop new methods for looking at the process of virus assembly at the cell surface. It is presently very difficult to look at whole cells in the electron microscope as they are too thick for the electrons to penetrate. We will use a new technique - Focussed Ion Beam milling (FIB) to prepare thin sections of frozen cells that will allow us to image RSV as it assembles. This will allow us to see whether certain components of the cell itself are co-opted by the virus to help its assembly and may also highlight possible targets for new medicines.

Moore's Law, the touchstone for advances in microelectronics, has bench-marked improvements in computer processing power over the past 40 years. The demand for continued increase is insatiable, but conventional technologies will succumb to fundamental limits on device size within a decade. My vision is removal of this roadblock to Moore's Law. My solution is to replace today's binary technologies with a range of intrinsically multi-state devices, thereby dramatically increasing performance without a need for further miniaturization. During my fellowship I will build a research group to explore the physics, materials and advances in characterisation techniques required to enable this transformation.

My core research programme takes as an exemplar resistive random access memory (Re-RAM), a genuinely "next-generation" technology that could make obsolete both conventional random access memory (RAM) and hard disk drives (HDDs). It offers in a single device the non-volatility and write-endurance of HDDs with the rapid access times of conventional RAM. Furthermore, it has the potential for 'stacked', 3-dimensional architectures and intrinsic multi-state functionality, which together could truly revolutionise data storage densities. Re-RAM materials undergo reversible chemical or structural changes under an applied voltage, giving a substantial change in device resistance that can function as a switch or stored data 'bit'. However, even basic understanding of the fabrication and nano-patterning protocols, let alone the underlying physics of the switching mode, is lacking for most candidate materials. Thus, it is not currently possible to build reliable multi-state devices. Moving the nanoscience to application can only be enabled by substantial research into processing and function. In many cases, the present uncertainty is simply because appropriate tools for nano-resolved characterization are only now becoming available. One of the most exciting aspects of this fellowship is my proposed development of in-situ electron microscopy characterization of prototypical devices during operation. For the first time, it will be possible to use electron microscopy to image devices and probe their chemistry on the nanometre scale whilst simultaneously applying voltage or current pulses to the sample. This advance will enable a full understanding of Re-RAM devices, their kinetics, scalability and their tolerance to defects. Ultimately, it will lead to improved device design and I confidently expect it to have a variety of beneficiaries outside of this programme. A further transformative aspect of the Fellowship is that I will augment Re-RAM far beyond the current state of the art by incorporating multiferroic materials. These materials retain well-defined electric and magnetic states that could be incorporated into the basic Re-RAM device but switched independently, further expanding the multi-state capability to truly transcend today's binary technologies. During this Fellowship, improved fabrication protocols will be developed and the combined functionality and intrinsic scalability of these new technologies will be assessed. The switching behaviour and structure-function correlation will be imaged directly, leading to unprecedented insights and, potentially, discovering a host of new and exciting physics.

Multiferroic materials have the potential to make a disruptive change to data storage in mass market consumer electronics. In principle, a multiferroic may hold a permanent magnetisation at the same time as a permanent electrical polarisation, with the two strongly coupled. This allows memory designers to produce arrays of bits in which digital data may be stored using an electric field (which is easy and takes little space), and read using a magnetic sensor (which is fantastically sensitive). Using such technology, digital information may be stored at much greater densities and thus hand held devices such as iPads, iPods and smartphones could operate with great memory and speed.

Bismuth ferrite (BiFeO3) is one of the few materials that promises to deliver magnetoelectric coupling at room temperature since it has both a permanent magnetisation and polarisation. Unfortunately, the magnetic ordering is very complex with only a weak ferromagnetic response. Moreover, the high conductivity ensures that the dielectric and ferroelectric properties cannot be optimised. Despite these problems, Prof. Reaney's research group at Sheffield have made significant advances by the use of the appropriate isovalent A-site (Nd3+) and aliovalent B-site (Ti4+) substituents in enhancing the ferromagnetic response and decreasing conductivity. Our initial results, however, show that there are many unusual features in the crystal structure which arise due to the doping mechanism which need to be understood if the properties are to be further improved.

The aim of the proposal therefore is to understand the doping mechanism in BiFeO3 on the the atomic scale, by examining ceramics at very high resolution in the scanning transmission electron microscope at the SuperSTEM facility, at the Daresbury Science and Innovation Campus. This will allow us to study the structure and chemistry of defects with atomic resolution and allow us to better understand which dopants are most effective in modifying the structure and properties of BiFeO3. The results will enable the CI at the University of Sheffield to improve ceramic formulations and processing parameters and thus enhance the magnetic and electrical properties, leading to the development of next generation memory storage devices.

Some atomic structures are just not amenable to traditional diffraction-based solution using X-rays or neutrons. One example of this is irregular or disordered layered structures, where the disorder on the nanoscale makes any interpretation of diffraction data extremely difficult. This is exactly the situation in lanthanum-doped zirconium-rich lead zirconate titanate where the unit cells often appear to have a period in one direction which is not a simple multiple of the number of building blocks of simple cells that they are made of (i.e. the full cell is incommensurate with the primitive cell). It appears that this happens because different layered structures can be formed and they can be stacked together irregularly. In this situation, the only way to determine the local atomic structure is via an imaging based technique with atomic resolution. This project will use high resolution scanning transmission electron microscopy at the world-leading EPSRC-supported SuperSTEM facility, which can image features down to below 1 Angstrom. In particular, the samples will be imaged using the High Angle Annular Dark Field technique, which is especially sensitive to heavy elements and which will consequently be invaluable for locating Pb and Zr ions; this will provide a powerful complement to HRTEM investigations being performed separately (also funded by the EPSRC under Grant Reference EP/H028218/1) which is more sensitive to oxygen ion locations. Images from both techniques will then be analysed quantitatively to extract atom positions and using images from more than one direction, we will then determine the three dimensional atom positions in each stacking sequence. This will then enable us to understand how the polarisation is ordered within the different stacking in order to produce antiferroelectric structures. This will provide a powerful demonstration of the capabilities of aberration corrected STEM in conjunction with quantitative data analysis to analyse nanoscale structures with atomic resolution, and will also lay the groundwork for future work on electric field induced phase transformations and possible applications of antiferroelectric lead zirconate titanate compositions.

Solar power is by far the most abundant renewable energy source. However, at present its use is limited by the high cost of solar cells, so that we continue to obtain most of our power from fossil fuels. Polymer (plastic) solar cells are an exciting research field that aims to address this problem, as polymer solar cells could be made by simple manufacturing processes such as roll to roll coating. The result would be much lower cost solar cells, with much lower energy of production. Most research to date has focussed on the efficiency of such solar cells, and good progress has been made, leading to efficiencies approximately two thirds of commercial amorphous silicon solar cells.

In this proposal we address the most important remaining issue, namely understanding and enhancing the lifetime of polymer solar cells. To do this we will combine advanced photophysical, morphological and chemical analysis of solar cells before, during and after operation to gain new insight into the factors controlling degradation of such cells. This will provide a solid foundation for developing strategies for extending the solar cell lifetime in the later part of the project.

The operation of polymer solar cells depends critically on the nanometre scale arrangement of the materials, so we will use sophisticated electron tomography techniques to study the nanoscale morphology and how it changes with device operation. This will be complemented by optical and electronic measurements performed in-situ on operating solar cells. A further innovation will be to make nanoscale perforation of an encapsulation layer and combine it with electron beam techniques to study local degradation with nanometre resolution. This challenging programme requires collaboration between world-leading research groups in St Andrews, Changchun, and Glasgow to access the range of expertise and facilities to make major progress, and will lead to a new UK-China collaboration.

Technologies that enable the efficient use of energy could have an enormous impact on the most pressing issues of today: global warming and the reliance on ever-dwindling supplies of fossil fuels.

The proposed research addresses this topical challenge through the investigation of the next generation of thermoelectric materials that harvest waste heat and transform it into useful electricity. In particular, the research is focused on thermoelectric materials that can operate at high temperatures, which is essential as the Carnot efficiency (the thermodynamic maximum) increases with temperature difference.

The scientific challenge is to optimise three competing material parameters; the Seebeck voltage; the electrical and thermal conductivity, and to do this in a material with good temperature stability.

The novelty of the proposed research derives from the use of ultra-high temperature synthesis to achieve temperature stability, and the synergistic exploitation of Zintl chemistry and interfaces in nanocomposites to obtain large thermoelectric figures of merit.

Zintl phases are key high-performance thermoelectric materials because the simultaneous presence of ionic and covalent regions enables a more independent optimisation of the thermoelectric parameters compared to electronically homogeneous materials. Two classes of promising Zintl-type phases have been identified, and the performance of outstanding bulk materials will be further enhanced through the use of interfaces in nanocomposites.

This ambitious and transformative research programme will contribute towards the development of high-performance thermoelectric materials operating at temperatures most suitable to power generation, enabling 20-30% energy conversion efficiencies. The research will also lead to an increased understanding of the relation between composition, structure and thermoelectric properties.

The behaviour of molybdenum gives a handle on the magnetic properties of these materials and we will combine this effect with Pb2+ cations that are known to give a strong distortion that gives control of the electric polarisation of these crystal structures. The lead(II) cation is strongly non-spherical and tends to displace the surrounding negatively charged ions to give a region of local charge separation. If these charges are ordered throughout a crystal then the material can interact with an electric field. Such ferroelectric behaviour is the basis for high speed memory. We plan to combine this electric polarisation with the magnetic ordering observed in molybdates and so obtain materials which can be switched between different magnetic and electric states by magnetic and electric fields. These multiferroic materials would have multiple states and so hold out the promise of storing information at a much higher density than current binary methods.

Growing concerns regarding the cost of energy as well as the sustainability of the current industrial and economic infrastructure in front of global population increase have made the development of transformative, sustainable technologies capable of supporting improved industrial and economic models an urgent priority of mankind as a whole. Crucial for these technological developments is the definition and understanding of novel materials which, as previously happened in human history, could unlock new scientific and technological horizons and positively impact across society, economy and politics. These elements have turned research in transformative, multifunctional materials into a priority of funding agencies and Industry both in UK and world-wide.

Very recently, a new class of multifunctional materials, topological insulators, has started to receive scientific attention due to their appealing physical properties with potential applications in a broad range of areas as diversified as energy storage, biosensing and quantum computing. The scientific interest in these materials originate from the realisation that, unlike the vast majority of known materials, topological insulators can conduct current extremely well (even as well as superconductors) through their surfaces but not through their bulk. Furthermore, due to quantum mechanical laws governing the relationship between the (crystal) momentum and spin of electrons in a solid, the surfaces of topological insulators could be used to transport information without the need of moving charge (as it happens in contemporary electronics devices) with the net result of no energy or information dissipation.

The breadth of the scientific challenges accompanying research in topological insulators, and the potentially ground-breaking impact that their development could generate in very diverse technological fields readily define one of the contemporary frontiers in interdisciplinary research at the boundary between Physics, Chemistry, Engineering, Medicine and Health Sciences. This in turn calls for a multidisciplinary research approach and, almost immediately, uncovers two limitations of the current research structure in the limited connections existing between diversified research communities, and in the lack of a common language to allow effective knowledge transfer and organisation.

Prompted by these considerations, and compatibly with the available budget, we will take topological insulators as a case study of multifunctional material to establish a multi-disciplinary research platform and pioneer:
(i) The creation of a common research language by bringing together researchers with diversified skill sets and expertise in solid state and surface chemistry, magnetism and biosensing, electron microscopy, computational chemistry, catalysis and photocatalysis, electron transport and superconductivity.
(ii) Novel and self-contained research protocols in materials science where all the steps including synthesis, doping, surface analysis, electron transport measurement and first principles interpretation of data will be executed with the aim of favouring expertise mixing and practice-based understanding of the actual limitations and potential of the methods used by one project partner in the research field of the others.
(iii) Novel research in the potential of chemical doping for improved topological insulators, and in their chemical stability to environmental agents.
(iv) Preliminary study about the potential of multiferroic material for (photo-)catalytic application for a future grant application.

At the end of the grant, the platform will have defined a common language and acquired a broad range of expertise and the cohesion needed to develop full scale grants that will not be limited to modification of already existing (however interesting) materials, but will tackle research in novel, sustainably generated, environmentally non-hazardous multifunctional materials.

The study of spin-transfer torque at a magnetic domain wall continues to be one of the most vibrant areas of research in spintronics, motivated by the prospect of novel memory and logic systems and devices. At heart, the phenomenon is based on a fundamental law of nature: conservation of angular momentum. As an electron moves, as part of a flow of electrical current, through a magnetic domain wall, the direction of magnetisation around it will rotate from that in the first domain to that in the second. The magnetic moment on that electron, which arises from its spin angular momentum, will have to rotate accordingly. This results in a change of angular momentum on the electron by a single quantum unit. This change is compensated for by an equal change in the magnetisation of the metal that is carrying the current. The outcome is that if enough electrons pass through a domain wall, the 'electron wind' will push the wall along, just as a sail is blown along by wind in the atmosphere. The potential for using this effect to write and manipulate data represented magnetically in the next generation of nanoelectronics has lead to proposals for device architectures such as IBM's racetrack memory.

At present, research in the field is overwhelmingly dominated by a single material and sample architecture: the lithographically patterned Permalloy nanowire. (Permalloy is a magnetically soft alloy of nickel and iron.) This is in spite of the fact that such nanostructures will probably not form the basis of any eventual device: the domain walls within them are too wide, too complex, and insufficiently rigid. Very high current densities, within an order of magnitude of the point of wire breakdown through electromigration, are needed to move them. From the point of view of basic research, it is clear that only a very restricted number of the possibilities for domain walls in nanowire systems has been investigated with any rigour. We will carry out a wide-ranging study of nanowires fabricated from multilayer films, drawing on years of experience in the preparation and study of such materials. Our attention will be focussed on two main classes of magnetic multilayer.

The first class is the so-called synthetic antiferromagnet. Here two magnetic layers sandwich a thin metal spacer layer, through which they are coupled so that their magnetic moments prefer to lie in opposite directions. The lack of a net magnetic moment means that such structures are impervious to moderate magnetic fields and can be packed densely together on a chip without interacting, both attractive for spintronic technologies. Moreover, we have carried out preliminary micromagnetic simulations, which predict narrow, simple domain walls in such structures.

The second class is multilayers in which the magnetisation lies perpendicular to the film plane. Recent results that we (and others) have obtained on these systems show that the efficiency of the spin-torque effect is roughly one hundredfold larger in these materials than in Permalloy - but that the defects in the materials lead to wall pinning effects that are larger by the same amount, so that huge current densities are still required. Here we will study the nature of the defects and so learn how to eliminate them, allowing such devices to operate with currents up to one hundred times smaller, leading to ten thousand times less power consumption.

We will also investigate the control of the spin-torque effect using local electrical gates, making use of another recent discovery: the fact that in such thin perpendicular layers, a suitable structure incorporating an interface with a dielectric can give rise to electric fields acting as effective magnetic fields on moving electrons, giving rise to a new spin-torque effect through spin-orbit interactions. This will give control of domain wall pinning with a fine spatial and time resolution using voltages, giving the prospect of novel device architectures.

The aim of this project is to develop a detailed physical understanding of the thermodynamic and kinetic behaviour of precipitation in high manganese austenitic steels and to provide essential data for the modelling of technologically important (iron-carbide and transition-metal-carbide) precipitation processes in this new generation of high strength alloys. No equivalent data is to be found anywhere in the existing literature. New precipitation models will be validated and published in a form which can easily be integrated with existing codes.