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Ultra-Sensitive Graphene Device For Spintronics

27 June 2011 CNR-Consiglio Nazionale delle Ricerche

A European team of researchers has developed a graphene-based device capable of detecting tiny magnetic fields with a record sensitivity down to the stray field of few magnetic molecules. The researchers have used graphene as a kind spider’s web to chemically trap the molecules and detect their magnetization at the same time. This breakthrough in spintronics opens the ways to applications for ultra-high density storage memories and for molecular sensors.

The study is published this month in the journal Nano Letters. The work has been performed by scientists from the S3 Center of Istituto Nanoscienze–Cnr, the Insitut Néel – CNRS, and the Karlsruhe Institute of Technology.

Magnetic molecules, nano-magnets only few billionth of meter small, are considered very promising for spintronics (electronics exploiting also the spin of the electron), since they can store a bit of information in a very small volume. In order to develop a new generation of magnetic memories it is crucial to be able to “read” tiny units that will soon reach the molecular size.

The new ultra-sensitive device realized enables the magnetic reading at the molecular scale. “It is the first time that such tiny objects are detected”, says Andrea Candini, researcher at the Istituto Nanoscienze-Cnr, “just to make clear, the previous record of sensitivity has been beaten by a factor of 100”.

To realize the device, the team deposited magnetic molecules on a sheet of graphene, the one atom-thick layer of Carbon famous for its amazing properties. Graphene works as a sort of spider's web able to chemically trap the molecules, to capture their magnetic flux and generate a corresponding electrical signal. This result is the outcome of a 3-year long research.. “Firstly, we synthesized molecules suitable to graft the graphene honeycomb lattice, then we tailored the graphene sheet realizing a device of about 10 nanometers in size; finally, we performed electrical measurements at very low temperatures, in order to limit the noise ”.

According to the team of researchers, this result “shows that it is possible to use graphene coupled to magnetic molecules to store information, as.the new device works similarly to the spin valve present in a reading head of today's hard disks, but it is much smaller" says Andrea Candini, "We also foresee applications to detect bio-molecules marked with a single magnetic molecule, such as ultra-sensitive sensors to be integrated in a lab-on-a-chip. " Both of these objectives are in line with the goals of large-scale initiatives such as the Flagship Pilot Actions recently launched by the European Commission on related themes. 

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