Magnetism - Page 4

Researchers at Rice University found that graphene nano-coils possess natural electromagnetic properties and can help in scaling down electronics by possibly replacing common solenoids (wires coiled around a metallic core that produce a magnetic field when carrying current, turning them into electromagnets. Solenoids also serve as inductors, primary components in electric circuits that regulate current, and in their smallest form are part of integrated circuits). 

The researchers discovered that when a voltage is applied, current will flow around the helical path and produce a magnetic field, as it does in macro inductor-solenoids. These graphene coil-structures are even found to form naturally during graphite growth, so they don't require complicated configuration or assembly. The researchers believe it should be possible to isolate graphene coil formations from crystals of graphitic carbon (graphene in bulk form), but enticing graphene sheets to grow in a spiral would allow for better control of its properties. 

Scientists from the U.S. Naval Research Laboratory (NRL) have found a simple and robust means to magnetize graphene using hydrogen. They placed graphene on a silicon wafer and dipped it in cryogenic ammonia with lithium (as this is a quick and gentle method to add hydrogen atoms and make the surface ferromagnetic).

Part of a large array generated by electron-beam lithography, containing ferromagnetic hydrogenated graphene lattice and the 50 nm nonmagnetic squares

Once made, the magnetic graphene was of exceptional quality. The scientists claim that it was surprising how the partially hydrogenated graphene prepared by this method was so uniform in its magnetism and apparently didn't have any magnetic grain boundaries. The NRL group also showed that the magnetic strength could be tuned by removing hydrogen atoms with an electron beam. The impact of the electrons can break the chemical bond between the graphene and the hydrogen, removing the hydrogen from the surface.

Researchers at the University of California at Riverside found a way to introduce magnetism in graphene while still preserving electronics properties. This may represent a significant step forward in the use of graphene in chips and electronics, since doping in the past induced magnetism but damaged graphene's electronic properties. this method can also be used in spintronics - chips that use electronic spin to store data.

The scientists explain they have overcome the problem by moving a graphene sheet very close to an electrical insulator with magnetic properties, since placing graphene on an insulating magnetic substrate can make the material ferromagnetic without disturbing its conductivity. The magnetic graphene is said to acquire new electronic properties, and so new quantum phenomena can take place.

Spanish researchers discovered a way of using lead atoms and graphene to create a powerful magnetic field by the interaction of the electrons' spin with their orbital movement. The scientists believe that this discovery could come in handy for spintronics applications. 

The researchers from IMDEA Nanoscience, the Autonomous University of Madrid, the Madrid Institute of Materials Science (CSIC) and the University of the Basque Country say that the key to their discovery was intercalation of atoms or Pb islands below the hexagons of carbon that make up graphene. This brings about a significant interaction between two electron characteristics - their spin and their orbit.

Researchers from UC Berkeley, Florida International University (FIU) and the Georgia Institute of Technology demonstrated for the first time the presence of magnetic properties in graphene nanostructures at room temperature. Magnetic graphene could have potential applications in information processing, medicine and Spintronics. 

To achieve this they functionalized the graphene with nitrophenyl. The researchers thus confirmed the presence of magnetic order in nanoparticle-functionalized graphene. The graphene was epitaxially grown at Georgia Tech, chemically functionalized at UC Riverside and studied at FIU and UC Berkeley.

Researchers from the University of Manchester managed to create elementary magnetic moments in graphene and then switch them on and off. This is the first time magnetism itself has been toggled, rather than the magnetization direction being reversed. They say this is a major breakthrough on the way towards graphene based Spintronics transistor-like devices.

The new research shows that electrons in graphene condense around vacancies ("holes" in the graphene sheet created when some carbon atoms are removed) - and create small "electronic cloud". These clouds carry a spin, and the researchers managed to dissipate and then condense back those clouds.

Researchers from Spain have succeeded in giving graphene magnetic properties - they have basically managed to create a hybrid graphene surface that behaves like a magnet. This may enable graphene-based Spintronic devices.

A magnetic material is a material in which most electrons have the same spin. In order to achieve that, the researchers grew a graphene sheet on a ruthernium single crystal substrate. Then they evaporated TCNQ (tetracyano-p-quinodimethane, which acts as a semiconductor at very low temperatures) molecules on the graphene surface. The TCNQ molecule acquired long-range magnetic order.

One of graphene's intrinsic features is ripples, similar to those seen on plastic wrap tightly pulled over a clamped edge. Induced by pre-existing strains in graphene, these ripples can strongly affect graphene's electronic properties, and not always favorably.

If the ripples can be controlled, however, they can be used to advantage in nanoscale devices and electronics, opening up a new arena in graphene engineering: strain-based devices.

UC Riverside's Chun Ning (Jeanie) Lau and colleagues now report the first direct observation and controlled creation of one- and two-dimensional ripples in graphene sheets. Using simple thermal manipulation, the researchers produced the ripples, and controlled their orientation, wavelength and amplitude.