Can Graphene-Based Materials Be Magnetic?

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy

Abstract

Graphene - a monolayer of carbon atoms densely packed in a honeycomb lattice - was discovered by the applicants' group in 2004 and, since then, has established itself as one of the most remarkable materials available to condensed matter scientists today. It is only one atom thick but stable under ambient conditions and exhibits extraordinarily high crystal and electronic quality. The most important graphene physics originates from its very unusual electronic properties: In other conductors charge carriers are described quantum mechanically as electron waves obeying the Schrdinger equation (the wave equation of quantum physics) but in graphene electrons move according to the laws of relativistic quantum physics - the Dirac equation. Graphene has now become a real gold mine for searching for new fundamental phenomena, and it also offers numerous applications, ranging from smart materials to future electronics. Theory predicts a whole spectrum of magnetic phenomena in graphene, including several mechanisms for intrinsic ferromagnetism and spin-ordering effects that arise due to its low-dimensionality and Dirac-like spectrum. However, none of these effects has so far been explored experimentally. If confirmed, the existence of spin ordering in graphene will have important implications not only for understanding of this remarkable material but also for its various applications and the field of spintronics in general.We are also hoping that our experiments on graphene will help resolve the controversies surrounding recent findings of magnetism in the so-called unconventional magnetic materials (bulk graphite, fullerenes, some oxides and hexaborides). In these materials ferromagnetism has been detected despite the absence of any magnetic-moment-carrying atoms (usually ferromagnetic ordering requires the presence of atoms with partially filled d- or f- shells that have non-zero total spin) but the findings remain highly controversial and there are many uncertainties related to the presence of impurities and defects. Graphene, on the other hand, is an ultimately simple and clean experimental system (with no crystal defects and impurities) where the density of charge carriers can be controlled by gate voltage. Therefore it should allow unambiguous answers to questions related to magnetism in other graphitic materials, in which the inevitable presence of impurities and imperfections can obscure vital evidence or lead to artefacts.We have a unique combination of skills and experience to make this project a success. Indeed, the very small magnetic moments associated with the discussed phenomena, together with submicron-scale magnetic field gradients, make it very difficult to probe the signatures of magnetism by traditional methods but they can be readily observed using the high-resolution Bitter decoration technique available to the applicants. This technique has sufficient field sensitivity and wide temperature range and is known to provide unique - yet easy-to-interpret - information. We have established and been using the technique successfully to study submicron-scale magnetisation patterns in superconductors and some magnetic materials. The applicants' group also remains the world leader in studies of the physics and technology of graphene. We believe that the combination of the unique method and expertise, a new approach to the problem of magnetism without magnetic ions , and a new experimental way of studying the exceptional experimental system should ensure exceptional research outcome.

Publications

10 25 50
 
Description We have demonstrated, for the first time, that point defects in graphene, such as vacancies and adatoms, carry magnetic moments. This is very important for the understanding of spin propagation in graphene, as well as as a basis for any induced magnetism in this versatile material. Furthermore, we have elucidated the nature of these magnetic moments and shown that they can be switched 'on and of' by doping, i.e. simply adding or removing electrons from graphene. In principle this can be done using electric field doping which is important for spintronic devices.
We also clarified the nature of weak ferromagnetism often found in graphite as being due to magnetic contamination (magnetic nanoparticles introduced during fabrication).
Exploitation Route Our findings have important implications for operation of future spintronic devices. Defect-induced magnetism in graphene and its effect on the performance of graphene-based lateral spin valves is now studied by many research groups around the world. The impact of our pioneering studies funded by the award is clear from the corresponding citation record [282 and 73 citations for Nature Phys. 8,199 (2012) and Nature Commun. 4, 2010 (2013)]. Firthermore, this research led to our participation in Spintronics Workpackage of the EC-FET Graphene Flagship project.
Sectors Electronics,Manufacturing, including Industrial Biotechology

 
Description Findings of our research formed the basis of a world-wide search for potential applications of magnetic defects in graphene for control of graphene-based spintronic devices, such as lateral spin valves. Although these activities are still at the research stage (either in academic labs or in R&D divisions of commercial companies), the level of interest has been on the increase.
Sector Digital/Communication/Information Technologies (including Software)
Impact Types Cultural

 
Description EU FET Graphene Flagship, Work Package 6: Graphene Spintronics 
Organisation Chalmers University of Technology
Department Graphene Flagship
Country Sweden 
Sector Public 
PI Contribution The European Commission has chosen Graphene as one of Europe?s first 10-year, 1,000 million euro FET flagships. The mission of Graphene is to take graphene and related layered materials from academic laboratories to society, revolutionize multiple industries and create economic growth and new jobs in Europe. From 2013 the Graphene Flagship will coordinate 126 academic and industrial research groups in 17 European countries, with an initial 30-month-budget of 54 million euros. Graphene Spintronics work package will investigate graphene's potential for spin-based electronics, such as the realization of spin transistors or spin qubits, owing to the low intrinsic spin orbit interaction, and the possibility to make graphene ''magnetic' by controlled introduction of defects. Dr Grigorieva will lead task 6.2 (Intrinsic magnetism in graphene and its interaction with spin transport) and contribute to task 6.4 (Spin sensors and spin gating graphene devices). Initial funding (£190,000 for Manchester spintronics activity in 2013-2015) will be followed by further investment until 2023.
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation AMO GmbH
Country Germany 
Sector Charity/Non Profit 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation Graphenea S.A.
Country Spain 
Sector Private 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation International Iberian Nanotechnology Laboratory
Country Portugal 
Sector Public 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Country France 
Sector Public 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation RWTH Aachen University
Country Germany 
Sector Academic/University 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Marie-Curie ITN SPINOGRAPH 
Organisation University of Groningen
Country Netherlands 
Sector Academic/University 
PI Contribution My research team was the first to demonstrate that point defects in graphene, such as vacancies and adatoms, carry magnetic moments leading to pronounced paramagnetic response at low temperatures. Although such magnetic moments do not make graphene truly magnetic, they are expected to have a profound effect on spin propagation in graphene devices. Furthermore we demonstrated that these magnetic moments can be 'switched on and off' by doping graphene. In our work (funded by EPSRC) we showed that such switching can be achieved by chemical doping. Now we are trying to demonstrate that it is also possible to achieve using electric fields. This is potentially important for spintronic devices.
Collaborator Contribution Our partners provide theoretical support, expertise in fabrication of spintronic devices based on graphene and provide graphene samples where appropriate.
Impact in process
Start Year 2013
 
Description Study of irradiation-induced defects in graphene and their role in magnetism 
Organisation University of Helsinki
Country Finland 
Sector Academic/University 
PI Contribution Academic collaboration
Start Year 2009