Heteronuclear Metalloporphyrin Dimers for Molecular Spintronics

A spin valve is an electronic device that can switch between two states - one of low resistance and one of high resistance - in response to an external magnetic field. Spin valves have played an important role in shaping the information technology landscape since their first development in the late 1980s by dramatically increasing magnetic data storage capacities with applications as read heads in hard disc drives (HDD), magnetic sensors, and memory unit in magnetic random-access memories (MRAM). The development of spin valves is part of the research field of spintronics - short for spin electronics - which comprises devices that make use of the charge and spin of electrons. Spin is a quantum-mechanical property that takes two discrete values: spin-up or spin-down.
Traditional spin valves are three-layer devices in which two conductive magnetic layers are separated by a non-magnetic layer. If the magnetic moments of the two magnetic layers point in the same direction, the resistance of the device is low, which results in a high electric current. If the two magnetic moments point in opposite directions, the resistance increases leading to a smaller electric current. This behaviour is caused by the spin polarization of the electrons of the electric current when passing through the magnetic layers: all electron spins are oriented either "up" or "down" depending on the magnetic orientation of the layer. Only if the two magnetic layers favour the same spin polarization, electrons can travel though the device efficiently leading to the low resistance state and the generation of a net spin polarized current.
The relative orientation of the two magnetic moments can be changed by applying an external magnetic field. This allows for the magnetoresponsive switching between an on-state with high conductance and a low conductance off-state. The translation of changes in the magnetic environment into electronic information is the key concept behind the broad range of application of spin valves.
This project targets the rational design, synthesis and study of the electronic properties of a single-molecule spin valve. Individual molecules are the smallest stable structural building blocks with only a few nanometres in size. Therefore, the design of functional molecules that mimic the properties of macroscopic electronic components is fundamental for the ultimate miniaturization of electronic circuits to the nanometre scale. To date, such molecular circuits have been elusive, but the continuous demand for increasing computing powers and the inherent limits of present manufacturing techniques make the transition to a molecular electronics landscape highly desirable.
Our approach for the synthesis of a single-molecule spin valve is based on the combination of two molecular magnets and a conductive wire in a single molecule. The molecular magnets will generate a spin polarization in the current passing through the wire and - analogous to a traditional spin valve - both magnetic centres need to favour the same spin orientation to result in a strong current through the device. The realization of a single-molecule spin valve is an important step towards understanding fundamental structure property relationships in the design of molecular electronic devices. It also has potential applications as a magnetoresponsive switch in a molecular circuit and for the generation of spin polarized currents for the use in molecular quantum information storage and quantum computing.
This multidisciplinary project involves a wide range of techniques including chemical synthesis, theoretical modelling, spectroscopic measurements, magnetometry, and cryogenic charge transport measurements. The project falls within the EPSRC quantum technologies research area and is conducted in close collaboration between the Department of Chemistry and the Department of Materials at the University of Oxford.

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.