Superior spin transport in graphene hammocks
Researchers from the FOM Foundation and the University of Groningen have developed a technique to produce graphene bridges in the shape of a hammock. Through these bridges the researchers transmit spin currents based on the magnetic moment of electrons. Although the theoretical predictions are positive about the spin current in graphene, the experimental results have yet to meet these expectations. The freely hanging graphene bridges were, however, found to be superb conductors for spin current. The new technique is important for spintronics equipment, which use the spin current for information storage and transfer. The researchers published their results on 18 June 2012 online in Nano Letters.
Graphene, a layer of carbon just one atom thick, is a highly promising material for spintronics. The difference between spintronics and electronics is in the information carriers: in electronics it is the charge of the electron and in spintronics the orientation of the magnetic moment of an electron, the spin. This is a relatively new field of research that could lead to new types of magnetic devices for data storage and transfer, which consume less energy and have a longer life.
High expectations
The two most important parameters for spintronics are the spin life expectancy – in other words how long spins can retain the same orientation – and the distance these spins can cover before they lose their information (spin relaxation distance). Although it has been theoretically predicted that spins in graphene will have a long life expectancy and relaxation distance, experimental observations have up until now failed to demonstrate this. The factors that limit spin transport in graphene remain unclear.
Hammock
In an effort to identify the limitations of graphene spintronics and to understand how spins behave in pure graphene, the researchers studied spin transport in freely hanging graphene. In these devices the graphene hangs as a hammock between two contacts and this results in a superior charge transport. The spin current measured through these bridges reveals that spin transport is in fact limited by the part of the graphene that is still supported. The graphene in areas that are genuinely hanging freely is of a very high quality and therefore highly promising for future spintronics devices.
Reference
'Spin Transport in High-Quality Suspended Graphene Devices', M. H. D. Guimarães, A. Veligura, P. J. Zomer, T. Maassen, I. J. Vera-Marun, N. Tombros, and B. J. van Wees, Nano Lett.
DOI: 10.1021/nl301050a
Contact
Marcos H.D. Guimarães +31 (0) 50 363 45 64
Paul J. Zomer +31 (0) 50 363 48 80
Bart J. van Wees +31 (0) 50 363 49 33