Almost all modern electronic devices require memory devices for large scale data storage with the ability to write, store and access information. There are strong commercial drives for increased speed of operation, energy efficiency, storage density and robustness of such memories. Most large scale data storage devices, including hard drives, rely on the principle that two different magnetization orientations in a ferromagnet represent the "zeros" and "ones". By applying a magnetic field to a ferromagnet one can reversibly switch the direction of its magnetisation between different stable directions and read out these states / bits from the magnetic fields they produce. This is the basis of ferromagnetic media used from the 19th century to current hard-drives. Today's magnetic memory chips (MRAMs) do not use magnetic fields to manipulate magnetisation with the writing process done by current pulses which can reverse magnetisation directions due to the spin-torque effect. In the conventional version of the effect, switching is achieved by electrically transferring spins from a fixed reference permanent magnet. More recently, it was discovered that the spin torque can be triggered without a reference magnet, by a relativistic effect in which the motion of electrons results in effective internal magnetic fields. Furthermore the magnetisation state is read electrically in such MRAMs. Therefore the sensitivity of ferromagnets to external magnetic fields and the magnetic fields they produce are not utilised. In fact they become problems since data can be can be accidentally wiped by magnetic fields, and can be read by the fields produced making data insecure. Also the fields produced limit how closely data elements can be packed. Recently we have shown that antiferromagnetic materials can be used to perform all the functions required of a magnetic memory element. Antiferromagnets have the north poles of half of the atomic moments pointing in one direction and the other half in the opposite direction leading to no net magnetisation and no external magnetic field. For antiferromagnets with specific crystal structures we predicted and verified that current pulses produce effective field which can rotate the two types of moments in the same directions. We were able to reverse the moment orientation in antiferromagnets by a current induced torque and to read out the magnetisation state electrically. Since antiferromagnets do not produce a net magnetic field they do not have all the associated problems discussed above. The dynamics of the magnetisation in antiferromagnets occur on timescales orders of magnitude faster than in ferromagnets, which could lead to much faster and more efficient operations. Finally, the antiferromagnetic state is readily compatible with metal, semiconductor or insulator electronic structures and so their use greatly expands the materials basis for such applications. This proposal aims to develop a detailed understanding of current induced switching in antiferromagnets though a program of research extensive experimental and theoretical studies and to pave the way to exploitation of this effect in future magnetic memory technologies. We will develop high quality antiferromagnetic materials and smaller and faster devices. We aim to achieve devices in which the antiferromagnetic state has not disordered (single domain behaviour) which will have improved technical parameters and which will be ideal for advancing fundamental understanding. We also aim to demonstrate and study the manipulation of regions of antiferromagnets in which there is a transition between two types of moment orientation (domain walls) using current-induced torques. As well as electrical measurements we will directly study the magnetic order in the antiferromagnetic devices using X-ray imaging techniques and we will carry out extensive theoretical modelling.

In this project we aim to develop new materials for the selective removal and long-term sequestration of radioactive Sr-90. This is of importance in Japan to help in the clean-up activities around the Fukushima Daiichi Nuclear Power Plant and in the UK to help in the clean-up of legacy waste at the Sellafield site and elsewhere. Although materials exist for removing Sr-90 from contaminated water, all have some limitations and/or high cost and therefore basic research aimed towards making new and improved materials is justified. The ideal adsorbent would be highly selective for Sr-90 in the presence of larger amounts of competitive cations (e.g. Ca, Mg, Na or K), be stable and effective over a large pH range, have a good capacity for Sr-90, be reusable, be easily made in bulk at low cost and have a simple and proven route to a safe and stable wasteform after its end of use. We target materials that have the potential to fulfil all of these criteria based on preliminary synthesis work already done in Japan (Shinshu and Tohuku Universities) with essential research in the UK supporting the characterisation and understanding of how the materials work (Diamond Light Source) and the production of wasteforms after use (University of Sheffield).

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Commercial catalysts are often based on metallic nanoparticles which have unusual and highly reactive properties due to their high proportion of surface atoms as compared to buried ones. Catalytic reactions occur at or just below surfaces and are helped by the crystal surface having defect sites and kinks. The exact architecture of the kinks can help in molecular recognition between the catalyst and its substrate, and help to make a particular form of the product molecule (called an enantiomer) over its mirror image 'twin'. Industry needs enantiomeric selectivity, and also better ways to make C-C bonds; both would become possible using a new type of nanoparticle based on bacteria. It is difficult to make nanoparticles chemically as they want to aggregate. When this happens the special properties are lost. Usually 'helper' chemicals ('passivant ligands') are needed. Bacteria can overcome this need. They can biomanufacture nanoparticles using enzymes and also support the nanoparticles by providing their own passivants. The catalytic bionanoparticles can be employed as catalysts by using the metallised bacteria as small (~2 microns) bodies in suspension (they can be recovered using a magnet), or by growing them first as a biofilm on (e.g) beads or monoliths and then metallising to form a catalytic nano-coating. Nothing is known yet about the surface structures of the bionanocrystals but they are excellent catalysts. It is known elsewhere that the application of dielectric fields (such as microwaves) can alter crystal surfaces (to make new, or different defects and kinks) or align crystals so that their most active faces point outwards. Nobody has applied dielectric fields to manipulate catalytic nanoparticles, especially not BIOnanoparticles, and we hope to make a completely new class of materials(superbionanocatalysts). We will test these in 4 important reactions where there are strong industrial needs: (a) enrich for a particular product in a mixture; (b) do a reaction which specifically needs NANOparticles; (c) do a reaction where we want an enantiomeric selection; (d) do a reaction which underpins commercial fertiliser production worldwide but usually needs very high temperatures and pressures. (a-c)usually use precious metal catalysts and (d) uses a catalyst based on iron; in the nanoworld these can often be used interchangeably (or together) because the same atomic-scale processes are involved. Effects of this are seen in magnetic (as well as catalytic) properties (a very useful diagnostic probe), while another facet is unravelled via an electrochemical 'dialogue' between the nanocrystal and the experimenter. These become even more interesting when the bacteria make 'bimetallics' (combining 2 metals); these often have greatly enhanced properties. We will look at bio-bimetallics for catalysis and also as fuel cell catalysts to make clean energy. Reactions involving Fe catalysts are special. They depend on the exact type of Fe used (the mineral phase); bacteria can make specific mineral phases to order. The catalytic reaction uses an activated form of hydrogen which normally only happens at high temperatures; small particles of ferric oxide are partially reduced by the active H to give some Fe metal (the catalyst; detected magnetically). Dielectric processing can also activate H, but at a much lower temperature, saving energy. Commercially, H is made from 'cracking' natural gas but this H contains traces of catalyst poisons. Biologically-made H is poison-free and the use of Bio-H will also help to extend catalyst life. We will make new, robust, superior, catalytic materials but, importantly, we will also relate the new crystal and nano structures to improved functions, applying a full range of solid state analytical methods to complement the magnetic and electrochemical ones. By understanding pivotal molecular processes in the nanoworld we can then design better catalysts for other commercial applications too.