#NRL Researchers First to Detect Spin Precession in Silicon nanowires Scientists at the U s. Naval Research Laboratory (NRL) have reported the first observation of spin precession of spin currents flowing in a silicon nanowire
and determined spin lifetimes and corresponding spin diffusion lengths in these nanoscale spintronic devices. The spin currents were injected electrically
and detected using ferromagnetic metal contacts with a tunnel barrier consisting of single layer graphene between the metal and silicon NW.
and detect spin appear as blue, the gold ohmic reference contacts appear as yellow, and the green line is the silicon nanowire transport channel.
The NRL research team observed spin precession (the Hanle effect) for both the spin-polarized charge near the contact interface and for pure spin currents flowing in the NW channel.
The latter unambiguously shows that spins have been injected and transported in the Si NW. The use of graphene as the tunnel barrier provides a low-resistance area product contact
Including electron spin as an additional state variable offers new prospects for information processing, enabling future nonvolatile, reprogrammable devices beyond the current semiconductor technology roadmap.
Silicon is an ideal host for such a spin-based technology because its intrinsic properties promote spin transport,
Realization of spin-based Si NW devices requires efficient electrical spin injection and detection, which depend critically on the interface resistance between a ferromagnetic metal contact and the NW.
Researchers have shown standard oxide tunnel barriers to provide good spin injection into planar Si structures,
and used a graphene tunnel barrier contact that produces excellent spin injection and also satisfies several key technical criteria:
The use of multilayer rather than single layer graphene in such structures may provide much higher values of the tunnel spin polarization because of band structure derived spin filtering effects predicted for selected ferromagnetic metal/multi
a spintronic circuit needs a well-controlled source of spin-polarized electrons that are injected into a transport channel material,
a well-defined method of controlling the spin through the material, and a system to detect the spin signal.
Additionally it requires a transport channel material with long spin lifetimes because (polarized) spins fade away (i e.,
, become randomized) and lose their information during transport, unlike electric charges. Compared to manipulating populations of moving electrons through a conventional semiconductor,
controlling electron spins consumes much less energy and has the further advantage that its information content is on-volatile
because the information is moved and stored in the form of magnetic states, it doesn disappear
Spin-based devices integrated with organic materials are expected to have low fabrication costs, light weight, and mechanical flexibility;
because the interface plays a critical role in determining the efficiency of spin injection and detection.
Cobalt is one of most widely used materials for spin injection/detection and so is Alq3 for spin transport.
Project Leader Christina Hacker elaborates: obalt surfaces are really interesting for electronic applications. If we can place molecular layers on them,
to examine the spin characteristics. The SAMS altered the spin magnetic moment, morphology, and energy band alignment of the materials differently depending on the SAM being studied.
In a critical finding, the data imply that the SAMS reduced the molecular hybridization between Co and Alq3,
and, furthermore, enhanced the spin magnetic moment of Co at the interface which is expected to improve spin polarization at the point of spin injection into an organic semiconductor,
Alq3. Hyuk-Jae Jang, the leader of this study, explains the significance: he interface between two different materials is very important in determining the performance and efficiency of electronic devices.
Particularly from the XMCD measurements, we found that the spin polarization can be enhanced at the interface by simple interface engineering.
This is helpful in efficient injection of the spin-polarized charge carrier from ferromagnetic materials to organic materials.
we need spin injection, spin transport, and spin detection, Jang explains. ur latest work with SAMS only concerns the interface relevant to the spin injection part.
The next step should be to find a better medium for spin transport since only short-distance couple of hundred nanometersf spin transport has been demonstrated in organic materials such as Alq3 so far.
There have been studies suggesting that long-distance spin transport in organics is achievable. Our grand plan is to make a whole device and show really long-distance (in this tiny device,
over a micrometer) spin transport through an organic semiconductor. r
#Expert: Editing stem cell genes will evolutionizebiomedical research Applying a dramatically improved method for ditinggenes to human stem cells,
University of Wisconsin-Madison neuroscientist Su-Chun Zhang has shown a new way to silence genes in stem cells and their progeny at any stage of development.
one of several ongoing particle physics experiments at the laboratory. LHCB studies antimatter and its relationship to matter.
The team electron spin resonance (ESR) probe takes a large-scale technique used for decades as a way to explore the overall properties of bulk materials
#Scientist discovers magnetic material unnecessary to create spin current It doesn happen often that a young scientist makes a significant and unexpected discovery,
What he foundhat you don need a magnetic material to create spin current from insulatorsas important implications for the field of spintronics and the development of high-speed,
low-power electronics that use electron spin rather than charge to carry information. Wu work upends prevailing ideas of how to generate a current of spins. his is a discovery in the true sense
said Anand Bhattacharya, a physicist in Argonne Materials science Division and the Center for Nanoscale Materials (a DOE Office of Science user facility),
One such method is to separate the flow of electron spin from the flow of electron current
To create a current of spins in insulators, scientists have kept typically electrons stationary in a lattice made of an insulating ferromagnetic material, such as yttrium iron garnet (YIG).
the spins begin to ove? that is, information about the orientation of a spin is communicated from one point to another along the lattice,
much in the way a wave moves through water without actually transporting the water molecules anywhere.
Spin excitations known as magnons are thought to carry the current. Wu set out to build on previous work with spin currents,
expanding it to different materials using a new technique he developed. He worked on making devices a thousand times smaller than the typical systems used,
in a paramagnet the spins aren aligned as they are in a ferromagnet. They generate no magnetic field, produce no magnons,
and there appears to be no way for the spins to communicate with one another. But to everyone surprise, the spin current was stronger in the GGG than it was in the YIG. he spins in the system were not talking to each other.
But we still found measurable spin current, says Wu. his effect shouldn happen at all. The next step is to figure out why it does. e don know the way this works
said Bhattacharya. here an opportunity here for somebody to come up with a theory for this.
the objects that are moving the spin are not what we typically understand. In the meantime, said Wu, ee just taken ferromagnetism off its pedestal.
harnessing particle physics to work faste o
#HOLY SEA SNAILS! Their TEETH are strong enough to build a plane Forget the Killer Rabbit from Monty python,
According to the study co-author Matthew Charles, a particle physicist at The french National Center for Scientific research LPNHE laboratory at the University of Paris VI
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