Soft chemical routes to novel magnetoelectric materials

More and more, we are seeing that combining useful and fascinating phenomena into a single, multifunctional material is driving the development of new advanced materials. Most interesting are properties that interact mutually to result in cooperative effects. Magnetoelectric multiferroic materials are simultaneously ferromagnetic (containing lined up magnetic dipoles of north and south poles) and ferroelectric (containing lined up electric dipoles made of positive and negative charges), meaning that they display a spontaneous magnetisation that can be reoriented by an applied magnetic field, and a spontaneous electric polarisation that can be reoriented by an applied electric field, within a single phase.
Besides scientific interest in their fundamental physical properties, novel multiferroic materials not only offer all the potential applications of ferromagnetic and ferroelectric materials, but also open the door to a range of other multifunctional applications. The most exciting of these is the ability to control the magnetic properties of a phase with an electric field, making technology which relies of magnetism more energy efficient. However, these materials have proven to be extremely challenging to synthesise, since the presence of one constituent ferroic property often precludes the onset of the other. As such, research has focussed on developing new approaches that can be used to design these materials.
The perovskite phase is an ideal system within which to study these properties, as the structure is flexible and can accommodate a range of elements. The cubic perovskite has the general formula ABX3, where the A-site ion occupies the corners of the lattice and the B-site ion occupies the centre of an octahedron, whilst six X-ions are positioned on the vertices. Recently, considerable effort has been made to exploit the cooperative rotations and tilts of the BX6 octahedra since they are ubiquitous in the perovskite structure and can be controlled through careful chemical substitution. Most importantly, the octahedral rotations couple strongly to the magnetic and electronic properties of the material. A novel mechanism, coined the 'trilinear coupling mechanism', which takes advantage of the rotation patterns of layered perovskites, has been investigated as a strategy to induce ferroelectricity in such materials.
The overarching aim of this project is to synthesise novel magnetoelectric multiferroic perovskite materials, exploiting the trilinear coupling mechanism to induce ferroelectricity and soft synthetic routes to obtain phases that would not be accessible using traditional ceramic solid-state methods, such as extremely high temperatures. More specifically, a series of distorted layered fluoride-perovskite phases will be synthesised. Existing literature on layered fluoride phases is scarce, since their oxide analogues tend to be more stable and as such, easier to synthesise. Because of this, novel solution-based synthetic methods will be employed in combination with solid-state techniques to obtain new phases. These materials will be studied using very high intensity x-rays and neutrons, which are necessary as the octahedral rotations and tilts being studied are small compared to the rest of the material.
This project falls within the EPSRC Physical sciences research area, and is co-supervised by Professor Stephen Blundell from the Department of Physics, Oxford University.

The primary impact of the OxICFM CDT will be the highly-trained world-class scientists that it delivers. This impact will encompass both the short term (during their doctoral studies), the medium term (subsequent employment) and ultimately the longer timescale defined by their future careers and consequent impact on science, engineering and policy in the UK.

The impact of OxICFM students during their doctoral studies will be measured by the culture change in graduate training that the Centre brings about - in working at the interface between inorganic synthesis and manufacturing, and fostering cross-sector industry/academia working practices. By embedding not only from larger companies, but also SMEs, we have developed a training regime that has broader relevance across the sector, and the potential for building bridges by fostering new collaborations spanning enormous diversity in scientific focus and scale. Moreover, at a broader level, OxICFM offers to play a unique role as a major focus (and advocate) for manufacturing engagement with academic inorganic synthetic science in the UK.

From a scientific perspective, OxICFM will be uniquely able to offer a broad training programme incorporating innovative and challenging collaborative projects spanning all aspects of fundamental and applied inorganic synthesis, both molecular and materials based (40+ faculty). These will address key challenges in areas such as energy provision/storage, catalysis, and resource provision/renewal necessary to enhance the capability and durability of UK plc in the medium term. To give some idea of perspective, the output from previous CDTs in Oxford's MPLS Division include two start-up companies and in excess of 30 patents.

It is not only in the industrial and scientific realms that students will have impact during their timeframe of their doctorate. Part of the training programme will be in public engagement: team-based challenges in resource development/training and outreach exercises/implementation will form part of the annual summer school. These in turn will constitute a key part of the impact derived from the CDT by its engagement with the public - both face-to-face and through electronic/web-based media. As the centre matures, our aspiration is that our students - from diverse backgrounds - will act as ambassadors for the programme and promote even higher levels of inclusion from all parts of society.

For our partners, and businesses both large and small in the manufacturing sector, it will be our students who are considered the ultimate output of the OxICFM CDT. Our programme has been shaped by the need of such companies (frequently expressed in preliminary discussions) to recruit doctoral graduates who can apply themselves to a broad spectrum of multi-disciplinary challenges in manufacturing-related synthesis. OxICFM's cohort-based training programme integrates significant industry-led training components and has been designed to deliver a much broader skill set than standard PhD schemes. The current lack of CDT training at the interface of inorganic chemistry and manufacturing (and the relevance of inorganic molecules/materials to numerous industrial sectors) heightens the need for - and the potential impact of - the OxICFM CDT. Our students will represent a tangible and valuable asset to meet the long-term skills demand for scientists to develop new materials and nanotechnology identified in the UK Government's 2013 Foresight report.

In the longer term, the broad and relevant training delivered by OxICFM, and the uniquely wide perspective of the manufacturing sector it will deliver, will allow our graduates to obtain (and thrive in) positions of significant responsibility in industry and in research facilities/institutes. Ultimately we believe that many will go on to be future research leaders, driving innovation and changing research culture, and thereby making a lasting contribution to the UK economy.