Synopsis:
Nanotechnology: Nanomaterials: Graphene: Graphene:
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that technology uses electrically conducting inks made from a pure-carbon material called graphene, which is basically the same stuff as the walls of carbon nanotubes
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This technique, made possible through the use of graphene, results in extremely fast response times of tenths of a second,
These nanoelectronic graphene vapor sensors can be embedded completely in a microgas chromatography system which is the gold standard for vapor analysis,
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Molybdenum disulfide isn t quite as flat as graphene the atom-thick form of pure carbon
When viewed from above it looks like graphene with rows of ordered hexagons. But seen from the side three distinct layers are revealed with sulfur atoms in their own planes above and below the molybdenum.
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Now his team has combined the dots with tiny sheets of graphene. The result is a hybrid material that could make it much cheaper to generate energy with fuel cells.
and excellent conductivity between GQDS provided by the graphene base. The boron and nitrogen collectively add more catalytically active sites to the material than either element would add alone. he GQDS add to the system an enormous amount of edge
which permits the chemistry of oxygen reduction one of the two needed reactions for operation in a fuel celltour says. he graphene provides the conductive matrix required.
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#Canâ graphene transform an apple into a doughnut? ETH Zurich rightoriginal Studyposted by Barbara Vonarburg-ETH Zurich on September 25 2014 More than 50 years ago a Russian physicist predicted that it s possible to transform from one topography to another.
and now researchers have used a double layer of graphene to demonstrate that it is indeed possible. e were able to prove the existence of a Lifshitz transitionsays Anastasia Varlet a doctoral candidate at ETH Zurich who was part of the research team that made the discovery.
nevertheless the researchers have achieved exactly that by using a double layer of graphene. The Lifshitz transition does not apply to objects in our normal environment;
when experimenting with the double layer of graphene: at a low water level there are three independent but equivalent lakes.
and initially the ETH team was had unaware it found the material that others had been looking for. e observed something strange in our measurements with the graphene sandwich construction that we were not able to explainsays Varlet.
To produce the sandwich construction Varlet enclosed the double layer of graphene in two layers of boron nitride a material otherwise used for lubrication
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The detector which is interconnected based on the carbon atoms in graphene can sense light over an unusually broad range of wavelengths including terahertz waves between infrared
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#Test keeps graphene pure enough for electronics Rice university rightoriginal Studyposted by Mike Williams-Rice on August 18 2014it s easy to accidentally introduce impurities to graphene
They expect the finding to be important to manufacturers considering the use of graphene in electronic devices.
Even a single molecule of a foreign substance can contaminate graphene enough to affect its electrical and optical properties says Junichiro Kono of Rice university.
The researchers used it as a substrate for graphene. Hitting the combined material with femtosecond pulses from a near-infrared laser prompted the indium phosphide to emit terahertz back through the graphene.
Imperfections as small as a stray oxygen molecule on the graphene were picked up by a spectrometer. he change in the terahertz signal due to adsorption of molecules is remarkablekono says. ot just the intensity
but also the waveform of emitted terahertz radiation totally and dynamically changes in response to molecular adsorption and desorption.
and changes over time. he laser gradually removes oxygen molecules from the graphene changing its density
Laser pulses generated coherent bursts of terahertz radiation through a built-in surface electric field of the indium phosphide substrate that changed due to charge transfer between the graphene and the contaminating molecules.
or any future device designs using graphene we have to take into account the influence of the surroundingssays Kono.
Graphene in a vacuum or sandwiched between noncontaminating layers would probably be stable but exposure to air would contaminate it he says.
and Masayoshi Tonouchi at Osaka s Institute of Laser Engineering are continuing to collaborate on a project to measure the terahertz conductivity of graphene on various substrates says Kono.
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This technique made possible through the use of graphene results in extremely fast response times of tenths of a second as opposed to the tens or hundreds of seconds typical in existing technology.
These nanoelectronic graphene vapor sensors can be embedded completely in a microgas chromatography system which is the gold standard for vapor analysis the researchers say.
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#Stretchy, bendy, stronger-than-ever graphene fiber Researchers have created a simple and scalable method of making strong,
GRAPHENE SLURRY FILM The researchers made a thin film of graphene oxide by chemically exfoliating graphite into graphene flakes,
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and then coated with a protective ultrathin graphene-like layer of carbon. Sandwiched between the two electrodes is a polymer film that acts as a reservoir of charged ions similar to the role of the electrolyte paste in a battery.
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#Car paint with graphene gets ice off radar domes Rice university rightoriginal Studyposted by Mike Williams-Rice on December 18 2013ribbons of ultrathin graphene combined with polyurethane paint meant for cars can keep ice off of sensitive military
because they re very poor conductors. nter graphene the single-atom-thick sheet of carbon that both conducts electricity and because it s so thin allows radio frequencies to pass unhindered.
and Volman recognized the potential. ristine graphene transmits electricity ballistically and would not produce enough heat to melt ice
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That involved crushing the coal and bathing it in acid solutions to break the bonds that hold the tiny graphene domains together. ou can'##t just take a piece of graphene
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engineers turned to atomically thin graphene. James Hone a mechanical engineering professor at Columbia University who co-led the project says the work emonstrates an application of graphene that cannot be achieved using conventional materials.
And it s an important first step in advancing wireless signal processing and designing ultrathin efficient cell phones. ur devices are much smaller than any other sources of radio signals
The combination of these properties makes graphene an ideal material for nanoelectromechanical systems (NEMS) which are scaled-down versions of the microelectromechanical systems (MEMS) used widely for sensing of vibration and acceleration.
In this new study published in Nature Nanotechnology the team took advantage of graphene s mechanical tretchabilityto tune the output frequency of their custom oscillator creating a nanomechanical version of an electronic component known as a voltage controlled oscillator (VCO.
The team built a graphene NEMS whose frequency was about 100 megahertz which lies right in the middle of the FM radio band (87.7 to 108 MHZ).
They used low-frequency musical signals (both pure tones and songs from an iphone) to modulate the 100 MHZ carrier signal from the graphene
While graphene NEMS will not be used to replace conventional radio transmitters they have many applications in wireless signal processing. ue to the continuous shrinking of electrical circuits known as Moore s Law today s cell phones have more computing
and their frequency can be tuned over a wide range because of graphene s tremendous mechanical strength. here is a long way to go toward actual applications in this areanotes Hone ut this work is an important first step.
and Shepard groups are now working on improving the performance of the graphene oscillators to have lower noise.
At the same time they are also trying to demonstrate integration of graphene NEMS with silicon integrated circuits making the oscillator design even more compact.
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what would happensays Pint. ypically researchers grow graphene from silicon-carbide materials at temperatures in excess of 1400 degrees Celsius.
But at lower temperatures 600 to 700 degrees Celsius we certainly didn t expect graphene-like material growth. hen the researchers pulled the porous silicon out of the furnace they found that it had turned from orange to purple or black.
but it was coated by a layer of graphene a few nanometers thick. They tested the coated material
Pint and his group argue that this approach isn t limited to graphene. he ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storagehe
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The researchers acknowledge that a solid two-dimensional sheet of graphene might be the perfect barrier to gas
but the production of graphene in such bulk quantities is not yet practical Tour says. But graphene nanoribbons are already there.
But the overlapping 200-to 300-nanometer-wide ribbons dispersed so well that they were nearly as effective as large-sheet graphene in containing gas molecules.
The Air force Research Laboratory through the University Technology Corp. the Office of Naval Research MURI graphene program and the Air force Office of Scientific research MURI program supported the research.
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#At super high temps, white graphene stops rust Atomically thin sheets of hexagonal boron nitride (h-BN) have the handy benefit of protecting
They also grew h-BN on graphene and found they could transfer sheets of h-BN to copper
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Scientists at Cornell and Germany s University of Ulm had been making graphene a two-dimensional sheet of carbon atoms in a chicken wire crystal formation on copper foils in a quartz furnace.
They noticed some uckon the graphene and upon further inspection found it to be composed of the elements of everyday glass silicon and oxygen.
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#Compact graphene device could shrink supercapacitors Monash University rightoriginal Studyposted by Emily Walker-Monash on August 5 2013monash U. AUS)# A new strategy to engineer graphene-based supercapacitors could make them viable
Graphene which is formed when graphite is broken down into layers one atom thick is very strong chemically stable and an excellent conductor of electricity.
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#Graphene#s jagged edge can easily slice cells Brown University right Original Study Posted by Kevin Stacey-Brown on July 10 2013brown (US) the jagged edges of tiny graphene sheets
The new insight may be helpful in finding ways to minimize the potential toxicity of graphene says Agnes Kane chair of the pathology and laboratory medicine department at Brown and one of the study s authors.
Discovered about a decade ago graphene is a sheet of carbon just one atom thick.
Their work on graphene started with some seemingly contradictory findings. Oddly shaped flakes Preliminary research by Kane s biology group had shown that graphene sheets can indeed enter cells
His models which simulate interactions between graphene and cell membranes at the molecular level suggested that it would be quite rare for a microsheet to pierce a cell.
The problem turned out to be that those initial simulations assumed a perfectly square piece of graphene.
When graphene is exfoliated or peeled away from thicker chunks of graphite the sheets come off in oddly shaped flakes with jagged protrusions called asperities.
Electron microscope images confirmed that graphene entered the cells starting at rough edges and corners. The experiments showed that even fairly large graphene sheets of up to 10 micrometers could be internalized completely by a cell.
But Kane says this initial study provides an important start in understanding the potential for graphene toxicity.
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#Graphene ribbons improve lithium ion batteries Anodes for lithium ion batteries built with ribbons of graphene perform better, tests show.
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##Quilted graphene is also super strong COLUMBIA U. US) Graphene, even if stitched together from many small crystalline grains,
Graphene consists of a single atomic layer of carbon, arranged in a honeycomb lattice. ur first Science paper,
in 2008, studied the strength graphene can achieve if it has no defectsts intrinsic strength,
and wee excited to say that graphene is back and stronger than ever. The study verifies that commonly used methods for postprocessing CVD-grown graphene weaken grain boundaries
resulting in the extremely low strength seen in previous studies. The team developed a new process that prevents any damage of graphene during transfer. e substituted a different etchant
and were able to create test samples without harming the graphene, notes the paper lead author, Gwan-Hyoung Lee,
a postdoctoral fellow in the Hone lab. ur findings clearly correct the mistaken consensus that grain boundaries of graphene are weak.
This is great news because graphene offers such a plethora of opportunities both for fundamental scientific research and industrial applications.
In its perfect crystalline form, graphene (a one-atom-thick carbon layer) is the strongest material ever measured
as the team reported in 2008o strong that, as Hone observes, t would take an elephant, balanced on a pencil,
to break through a sheet of graphene the thickness of Saran wrap. For the first study, the team obtained small, structurally perfect flakes of graphene by mechanical exfoliation,
or mechanical peeling, from a crystal of graphite. But exfoliation is a time-consuming process that will never be practical for any of the many potential applications of graphene that require industrial mass production. httpv://www. youtube. com/watch?
v=VSPWRC6RCVY Why so weak? Currently, scientists can grow sheets of graphene as large as a television screen by using chemical vapor deposition (CVD), in
which single layers of graphene are grown on copper substrates in a high-temperature furnace. One of the first applications of graphene may be as a conducting layer in flexible displays. ut CVD graphene is titchedtogether from many small crystalline grainsike a quiltt grain boundaries that contain defects
in the atomic structure, Kysar explains. hese grain boundaries can severely limit the strength of large-area graphene
if they break much more easily than the perfect crystal lattice, and so there has been intense interest in understanding how strong they can be.
The team wanted to discover what was making CVD graphene so weak. In studying the processing techniques used to create their samples for testing,
they found that the chemical most commonly used to remove the copper substrate also causes damage to the graphene,
severely degrading its strength. Their experiments demonstrated that CVD graphene with large grains is exactly as strong as exfoliated graphene,
showing that its crystal lattice is just as perfect. And, more surprisingly, their experiments also showed that CVD graphene with small grains
even when tested right at a grain boundary, is about 90 percent as strong as the ideal crystal. his is an exciting result for the future of graphene,
because it provides experimental evidence that the exceptional strength it possesses at the atomic scale can persist all the way up to samples inches
Strong, large-area graphene can be used for a wide variety of applications such as flexible electronics and strengthening componentsotentially,
a science fiction idea of a space elevator that could connect an orbiting satellite to Earth by a long cord that might consist of sheets of CVD graphene,
since graphene (and its cousin material, carbon nanotubes) is the only material with the high strength-to-weight ratio required for this kind of hypothetical application.
The team is excited also about studying 2d materials like graphene. ery little is known about the effects of grain boundaries in 2d materials
This is due to all the atoms in graphene being surface atoms, so surface damage that would normally not degrade the strength of 3d materials can completely destroy the strength of 2d materials. owever with appropriate processing that avoids surface damage,
especially graphene, can be nearly as strong as the perfect, defect-free structure. The Air force Office of Scientific research and the National Science Foundation supported the research c
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#Researchers discover 3d material that behaves like graphene This illustration depicts fast-moving, massless electrons inside cadmium arsenide.
and Berkeley Lab have found that cadmium arsenide could yield practical devices with the same extraordinary electronic properties as 2d graphene.
There is a quest to find graphene-like materials that are three-dimensional and thus much easier to craft into practical devices.
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#Graphene discovery: A low-end kitchen blender can make a high-end batch of this valuable material Blenders can be a great way to make smoothies or margaritas,
Researchers have figured out how to use ordinary kitchen blenders to create thin sheets of graphene, a marvelous high-tech material that is just one atom thick but 100 times stronger than steel.
Graphene is also an incredibly efficient conductor of heat and electricity. All of these qualities make it valuable for use in electronics and a variety of other applications,
but so far production of high-quality graphene has been limited to fairly small batches. This new discovery, published this week in the journal Nature Materials,
"This clearly shows that even very crude mixers can produce well exfoliated graphene, "the authors wrote in their paper.
This doesn't mean that your average person could start mixing up graphene in their kitchen the liquid and detergent need to be removed
it will be necessary to develop industrially scalable methods to produce large quantities of defect-free graphene."
graphene will find commercial applications in many areas from high-frequency electronics to smart coatings. Some important classes of applications,
such as printed electronics, conductive coatings and composite fillers, will require industrial-scale production of defect-free graphene in a process-able form."
They tell Nature they hope to be producing a kilogram of graphene a day by the end of the year
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#Graphene electrode promises stretchy circuits: Nature News A transparent, flexible electrode made from graphene could see a one-atom thick honeycomb of carbon first made just five years ago replace other high-tech materials used in displays.
It could even be used instead of silicon in electronics. Byung Hee Hong from Sungkyunkwan University in Suwon, Korea,
and his colleagues transferred a wafer-thin layer of graphene, etched into the shape needed to make an electrode, onto pieces of polymer.
The resulting films conduct electricity better than any other sample of graphene produced in the past. Until recently
high-quality graphene has been hard to make on a large scale. To produce their graphene, Hong and his colleagues used a technique that is well known in the semiconductor industry chemical vapour deposition.
This involves exposing a substrate to a number of chemicals, often at high temperatures. These chemicals then react on the surface to give a thin layer of the desired product.
The results in Hong's case were relatively large, high-quality films of graphene just a few atoms thick and several centimetres wide.
and by cooling the sample quickly after the reaction the researchers could produce up to ten single-atom layers of carbon in graphene's signature honeycomb pattern.
Because the layers of graphene are so thin the resulting electrodes are transparent, and Hong says that makes the material ideal for use in applications such as portable displays.
His team is also looking at using the graphene electrodes in photovoltaic cells. Easing the pain
Geim had predicted that chemical vapour deposition would be the best technique for making high-quality graphene films3.
"Hong thinks that graphene's most promising application will be to replace the silicon-based materials used in semiconductor technologies.
and to modify the conductivity of graphene nanostructures. Such applications could be some time off, says Geim."
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#Light pulses control graphene s electrical behavior Graphene, an ultrathin form of carbon with exceptional electrical optical and mechanical properties, has become a focus of research on a variety of potential uses.
But if the graphene starts out with high electron concentration the pulse decreases its conductivity the same way that a metal usually behaves.
Therefore by modulating graphene's electron concentration the researchers found that they could effectively alter graphene's photoconductive properties from semiconductorlike to metallike.
The finding also explains the photoresponse of graphene reported previously by different research groups which studied graphene samples with differing concentration of electrons.
We were able to tune the number of electrons in graphene and get either response,
To perform this study the team deposited graphene on top of an insulating layer with a thin metallic film beneath it;
by applying a voltage between graphene and the bottom electrode the electron concentration of graphene could be tuned.
The researchers then illuminated graphene with a strong light pulse and measured the change of electrical conduction by assessing the transmission of a second low-frequency light pulse.
In this case the laser performs dual functions. We use two different light pulses: one to modify the material and one to measure the electrical conduction.
This all-optical method avoids the need for adding extra electrical contacts to the graphene. Gedik the Lawrence C. and Sarah W. Biedenharn Associate professor of Physics says the measurement method that Frenzel implemented is a cool technique.
and reveal graphene's electrical response in only a trillionth of a second. In a surprising finding the team discovered that part of the conductivity reduction at high electron concentration stems from a unique characteristic of graphene:
its electrons travel at a constant speed similar to photons which causes the conductivity to decrease when the electron temperature increases under the illumination of the laser pulse.
Our experiment reveals that the cause of photoconductivity in graphene is very different from that in a normal metal or semiconductors,
therefore require increasing absorption efficiency such as by using multiple layers of graphene, Gedik says. Isabella Gierz a professor at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg Germany who was involved not in this research says:"
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They are also working on incorporating electronic nanomaterials, such as graphene, into plants. ight now, almost no one is working in this emerging field,
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The new findings using a layer of one-atom-thick graphene deposited on top of a similar 2-D layer of a material called hexagonal boron nitride (hbn) are published in the journal Nano Letters.
The hybrid material blocks light when a particular voltage is applied to the graphene, while allowing a special kind of emission and propagation,
Light interaction with graphene produces particles called plasmons while light interacting with hbn produces phonons.
The properties of the graphene allow precise control over light, while hbn provides very strong confinement and guidance of the light.
says, his work represents significant progress on understanding tunable interactions of light in graphene-hbn.
The work is retty criticalfor providing the understanding needed to develop optoelectronic or photonic devices based on graphene and hbn,
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Among nanomaterials, carbon-based nanoparticles such as carbon nanotubes and graphene have shown promising results, but they suffer from relatively low electrical conductivity,
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#Researchers use oxides to flip graphene conductivity Graphene a one-atom thick lattice of carbon atoms is touted often as a revolutionary material that will take the place of silicon at the heart of electronics.
By demonstrating a new way to change the amount of electrons that reside in a given region within a piece of graphene they have a proof-of-principle in making the fundamental building blocks of semiconductor devices using the 2-D material.
Moreover their method enables this value to be tuned through the application of an electric field meaning graphene circuit elements made in this way could one day be rewired dynamically without physically altering the device.
Chemically doping graphene to achieve p -and n-type version of the material is possible but it means sacrificing some of its unique electrical properties.
but manufacturing and placing the necessary electrodes negates the advantages graphene's form factor provides.
We've come up with a non-destructive reversible way of doping Rappe said that doesn't involve any physical changes to the graphene.
The team's technique involves depositing a layer of graphene so it rests on but doesn't bond to a second material:
Here we have graphene standing by on the surface of the oxide but not binding to it.
or gaining electrons the graphene says'I can hold the electrons for you and they'll be right nearby.'
Because the lithium niobate domains can dictate the properties Shim said different regions of graphene can take on different character depending on the nature of the domain underneath.
That allows as we have demonstrated a simple means of creating a p-n junction or even an array of p-n junctions on a single flake of graphene.
Such an ability should facilitate advances in graphene that might be analogous to what p-n junctions and complementary circuitry has done for the current state-of-the-art semiconductor electronics.
What's even more exciting are the enabling of optoelectronics using graphene and the possibility of waveguiding lensing and periodically manipulating electrons confined in an atomically thin material.
and the charge carrier density of the graphene suspended over it. And because the oxide polarization can be altered easily the type
and extent of supported graphene doping can be altered along with it. You could come along with a tip that produces a certain electric field
and the graphene's charge density would reflect that change. You could make the graphene over that region p-type
or n-type and if you change your mind you can erase it and start again.
Researchers make magnetic graphene More information: Nature Communications dx. doi. org/10.1038/ncomms713 3
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#Researchers make magnetic graphene Graphene a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice has many desirable properties.
Magnetism alas is not one of them. Magnetism can be induced in graphene by doping it with magnetic impurities
but this doping tends to disrupt graphene's electronic properties. Now a team of physicists at the University of California Riverside has found an ingenious way to induce magnetism in graphene while also preserving graphene's electronic properties.
They have accomplished this by bringing a graphene sheet very close to a magnetic insulator-an electrical insulator with magnetic properties.
This is the first time that graphene has been made magnetic this way said Jing Shi a professor of physics
and astronomy whose lab led the research. The magnetic graphene acquires new electronic properties so that new quantum phenomena can arise.
These properties can lead to new electronic devices that are more robust and multifunctional. The finding has the potential to increase graphene's use in computers as in computer chips that use electronic spin to store data.
Study results appeared online earlier this month in Physical Review Letters. The magnetic insulator Shi and his team used was yttrium iron garnet grown by laser molecular beam epitaxy in his lab. The researchers placed a single-layer graphene sheet on an atomically smooth layer of yttrium iron garnet.
In other words graphene simply borrows the magnetic properties from yttrium iron garnet. Magnetic substances like iron tend to interfere with graphene's electrical conduction.
The researchers avoided those substances and chose yttrium iron garnet because they knew it worked as an electric insulator
which meant that it would not disrupt graphene's electrical transport properties. By not doping the graphene sheet
but simply placing it on the layer of yttrium iron garnet they ensured that graphene's excellent electrical transport properties remained unchanged.
In their experiments Shi and his team exposed the graphene to an external magnetic field. They found that graphene's Hall voltage-a voltage in the perpendicular direction to the current flow-depended linearly on the magnetization of yttrium iron garnet (a phenomenon known as the anomalous Hall effect seen in magnetic materials like iron and cobalt.
This confirmed that their graphene sheet had turned magnetic. Explore further: Researchers find magnetic state of atoms on graphene sheet impacted by substrate it's grown on More information:
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