Graphene - Page 8

Researchers from Georgia State University (GSU) and the Georgia Institute of Technology (Georgia Tech) developed a new technique that enabled them to to study the spin characteristics of electrons using graphene.

The research team illuminating the graphene based device by microwaves (which causes the spin-splitting energy to equalize). The device’s resistance is altered when the microwave energy is absorbed by the device. This effect is small and difficult to measure normally, but by using Graphene, enabled them to actually witness this effect.

Researchers from the University of South Florida and the University of Kentucky have demonstrated a material in which the spins can be set in a controlled manner. The team suggest using cobalt atoms on a graphene sheet.

The researchers have used state-of-the-art theoretical computations to prove this.

Researcher Michel de Jong of the NanoElectronics group (MESA+) in the University of Twente (Netherlands) received a €1.5 million grant from the European Research Council to fund his Spintronics work (this is his second ERC grant). Michel de Jong is focusing on organic materials, in particular in Buckyballs (spherical C60 molecules held together by weak bonds) sandwiched between two magnetic materials.

Michel explains that these molecules have very little effect on electron spin, which is a great advantage as it enables them to store spin information for much longer periods of time than silicon. Buckyballs have also been used to create Graphene Quantum Dots.

Researchers from China's Fudan University say that graphene nanoribbons could potentially be used to create spin valves. They present a theoretic spin valve design that uses two hexagonal graphene "nanoislands" with zig-zag edges, which serve as the magnetic layers in the spin valve, connected by an armchair-type nanoribbon as the non-magnetic layer, through which the electrons can pass depending on the relative alignment of the spins in the nanoislands.

They calcualte that this design enables stable spin configurations at certain energies, and there will be stable configurations in which the islands are polarized either parallel or antiparallel with respect to each other — a necessary requirement for a spin valve.

The National Science Foundation (NSF) granted a four-year $1.85 million research project to UC Riverside researchers - to develop spin-based memory and logic chip. The researchers are working towards a magnetologic gate that will serve as the engine for the new technology - similar to the role of the transistor in conventional electronics.

The magnetic gate consists of graphene contacted by several magnetic electrodes. Data is stored in the magnetic state of the electrodes, similar to the way data is stored in a magnetic hard drive. For the logic operations, electrons move through the graphene and use its spin state to compare the information held in the individual magnetic electrodes.

Graphene can adsorb oxygen onto its surface (which changes graphene's electronic transport properties). This can be useful for Spintronics devices, but the adsorption is difficult to control. Researchers from the Tokyo Institute of Technology developed a way to control the adsorption of oxygen by applying an electric field to a Graphene-based field-effect transistor (FET).

via Graphene-Info

Scientists from The University of Nottingham, UK, developed a new self-assembly based method to create sulphur-terminated graphene nanoribbon within a single-walled carbon nanotube. They say that these ribbons have some interesting physical properties and they are suitable for applications in electronic and spintronic devices - more so than 'regular' graphene.

The team have demonstrated that carbon nanotubes can be used as nanoscale chemical reactors and chemical reactions involving carbon and sulphur atoms held within a nanotube lead to the formation of atomically thin strips of carbon, known as graphene nanoribbon, decorated with sulphur atoms around the edge.

Researchers from Europe developed a graphene based device that can detect magnetic fields with a record sensitivity (down to the stray field of few magnetic molecules, better than the previous record of sensitivity by a factor of 100). The graphene was used like a spider web to chemically 'trap' the molecules and detect their magnetization at the same time. This new development may enable ultra-high density Spintronics memory and molecular sensors.

Researchers from the University of Maryland (UMD) discovered that missing atoms in Graphene (called vacancies) act as tiny magnets. If you arrange the atoms in a certain way, you could get ferromagnetism - which can be useful in spintronics devices.

Researchers from the City University of Hong Kong managed to generate a spin current in Graphene, which could lead us to using Graphene as a spintronics device.

The scientists used spin splitting in monolayer graphene generated by ferromagnetic proximity effect and adiabatic (a process that is slow compared to the speed of the electrons in the device) quantum pumping. They can control the degree of polarization of the spin current by varying the Fermi energy (the level in the distribution of electron energies in a solid at which a quantum state is equally likely to be occupied or empty), which they say is very important for meeting various application requirements.