Elusive Spintronics Success Could Lead to Single Chip for Processing and Memory
Queen Mary, University of London (UK) and the University of Fribourg
(Switzerland) have shown that a magnetically polarised current can be
manipulated by electric fields.
Published this week in the journal Nature Materials, this
important discovery opens up the prospect of simultaneously processing
and storing data on electrons held in the molecular structure of
computer chips -- combining computer memory and processing power on the
same chip.
"This is especially exciting, as this discovery has been made with
flexible organic semiconductors, which are set to be the new generation
of displays for mobile devices, TVs and computer monitors, and could
offer a step-change in power efficiency and reduced weight of these
devices," said Dr Alan Drew, from Queen Mary's School of Physics, who
led the research.
'Spintronics' -- spin transport electronics -- has rapidly become the
universally used technology for computer hard disks. Designed in thin
layers of magnetic and non-magnetic materials, Giant Magnetoresistive
(GMR) spin valves use the magnetic properties, or 'spin', of electrons
to detect computer data stored in magnetic bits. In contrast, computer
processing relies on streams of electrically charged electrons flowing
around a tiny circuit etched into a microchip.
Dr Drew and his team have investigated how layers of Lithium Fluoride
(LiF) -- a material that has an intrinsic electric field -- can modify
the spin of electrons transported through these spin valves. He
explains: "While in theory, devices that combine electron charge and
spin are conceptually straightforward, this is the first time anybody
has shown it is possible to proactively control spin with electric
fields."
Professor Christian Bernhard, from the University of Fribourg Physics
Department, describes their successful technique: "Using the direct
spectroscopic technique Low Energy Muon Spin Rotation (LE-μSR), our
experiments have visualised the extracted spin polarisation close to
buried interfaces of a spin valve."
The experiments were performed at the Paul Scherrer Institute, the
only institution worldwide; where this technique is available. The
method employs the magnetic properties of muons -- unstable subatomic
particles. "In such an experiment the muons are shot into the material
and when they decay, the decay products carry information about the
magnetic processes inside the material," explains Professor Elvezio
Morenzoni from PSI, where the technique has been developed. "The unique
thing about low energy muons is that they can be placed specifically in a
particular layer of a multi-layer system. Thus using this method one
can study the magnetism in any single layer separately."
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