Spin@RT: Room Temperature Spintronics

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy


Spintronics is the name given to the integration of electron spin into electronics. The aim of spintronics is to control the spin so that it can be used in a new generation of electronic devices. Within this pursuit there is a great deal of interesting fundamental physics and this is where our efforts will be concentrated. Spintronics has been with us for several years where devices such as read-heads for hard discs are a commonplace example of a metal-based device. There is also considerable research effort on using semiconductors in spintronics, but for reasons made clear in the case, we shall concentrate on metal and oxide spintronic research. Spintronics has reached a stage where further significant progress requires a new generation of devices based on a qualitatively different physics. Our proposal has four major themes. In the first we propose to exploit the new idea that the coherence of electron wave functions may be preserved during the transport of charge and spin across the entire thickness of an epitaxial magnetic nanostructure. It was proposed that coherent transport could improve the magnetoresistance (MR) by more than an order of magnitude. The impact of such an improvement in MR alone on spintronic devices such as magnetic random access memory (MRAM) would be immense. In the second theme we intend to use the resolution of facility-based x-ray sources in an entirely new way, specifically, to observe the small but significant changes in the spin polarisation of a noble metal that result from injection of a spin-polarised current. This first direct measurement of spin accumulation in the diffusive regime will exploit our expertise in large area nano-device fabrication, the use of synchrotron radiation and high frequency measurements in micro-scale waveguides. In the third theme we will study the temporal and spatial coherence of the current-induced magnetic state of nano-pillar arrays using hitherto unexploited x-ray, neutron and time-resolved optical techniques to distinguish between analytical models for spin-transfer torque, and to understand the rich dynamic behaviour that has recently been reported. Finally, in the fourth theme, we will combine the growth of novel magnetoresistive materials with nano-fabrication, and use a powerful collection of magnetic characterisation tools to observe the current-induced motion of domain walls. This will allow us to resolve a number of critical but controversial issues such as the minimum current density required to induce wall motion, the intrinsic limit upon wall velocity, and the influence of edge structure
Description Spin@RT helped to establish a dominant position for the UK in metallic Spintronics. There are great opportunities to exploit this successful model in metals-based spintronics: new physics is developing in the form of pure spin currents that offer the real possibility of dissipationless spin transfer that can exert torque to reverse magnetic elements or drive new devices. The spin Hall effect is much larger in metals than in semiconductors and can be enhanced by careful alloying to increase the spin-orbit coupling on which the effect relies. High frequency dynamics is a very promising field where using spin torque to generate microwave energy relies on coupling many nano-oscillators to achieve useful power levels - of direct relevance to industrial exploitation. Domain wall spintronics is an extremely active area but virtually all that is known is based on transverse/vortex walls in Permalloy ribbons. Wall motion must be controlled and work in this consortium suggests that clever application of exchange biasing and artificial multilayer antiferromagnets can make serious inroads into understanding the limits of wall mobility and tailoring pinning potentials to control wall dynamics.
Exploitation Route Developing a shared vision of tomorrow's major challenges and opportunities with stakeholders: society, industry, universities and other partners. This will be possible by our extension of the collaboration with industry, increasing our engagement with schools, furthering our activity for public understanding (building on the Spin@RT Royal Society exhibit). We will establish an annual Showcase meeting for industry, government and education to promote research in spintronics.
Sectors Electronics

URL http://gow.epsrc.ac.uk/NGBOViewGrant.aspx?GrantRef=EP/D000572/1