News Scientists create the world’s thinnest magnet – University of California

The development of an ultrathin magnet that operates at room temperature could lead to new applications in computing and electronics such as high-density, compact spintronic memory devices and new tools for the study of quantum physics.

The ultrathinmagnet,which was recentlyreported in the journal Nature Communications, could make big advances in next-gen memory devices, computing, spintronicsand quantum physics. It was discovered by scientists at the Department of Energys Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley.

Were the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions, said senior authorJie Yao, afaculty scientist in Berkeley Labs Materials Sciences Division and associate professor ofmaterials science and engineering at UC Berkeley.

This discovery is exciting because it not only makes 2D magnetism possible at room temperature, but it also uncovers a new mechanism to realize 2Dmagneticmaterials, added Rui Chen, a UC Berkeley graduate student in theYao Research Groupand lead author on the study.

The magnetic component of todays memory devices is typically made of magnetic thin films. But at the atomic level, these materials are still three-dimensional hundreds or thousands of atoms thick. For decades, researchers have searched for ways to make thinner and smaller 2D magnets and thus enable data to be stored at a much higher density.

Previous achievements in the field of 2D magnetic materials have brought promising results. But these early 2D magnets lose their magnetism and become chemically unstable at room temperature.

State-of-the-art 2D magnets need very low temperatures to function. But for practical reasons, a data center needs to run at room temperature, Yao said. Our 2D magnet is not only the first that operates at room temperature or higher, but it is also the first magnet to reach the true 2D limit: Its as thin as a single atom!

The researchers say that their discovery will also enable new opportunities to study quantum physics. It opens up every single atom for examination, which may reveal how quantum physics governs each single magnetic atom and the interactions between them, Yao said.

The researchers synthesized the new 2D magnet called a cobalt-doped van der Waals zinc-oxide magnet from a solution of graphene oxide, zinc, and cobalt.

Just a few hours of baking in a conventional lab oven transformed the mixture into a single atomic layer of zinc-oxide with a smattering of cobalt atoms sandwiched between layers of graphene.

In a final step, the graphene is burned away, leaving behind just a single atomic layer of cobalt-doped zinc-oxide.

With our material, there are no major obstacles for industry to adopt our solution-based method, said Yao. Its potentially scalable for mass production at lower costs.

To confirm that the resulting 2D film is just one atom thick, Yao and his team conducted scanning electron microscopy experiments at Berkeley LabsMolecular Foundryto identify the materials morphology, and transmission electron microscopy (TEM) imaging to probe the material atom by atom.

X-ray experiments at Berkeley LabsAdvanced Light Sourcecharacterized the 2D materials magnetic parameters under high temperature.

Additional X-ray experiments at SLAC National Accelerator Laboratorys Stanford Synchrotron Radiation Lightsource verified the electronic and crystal structures of the synthesized 2D magnets. And at Argonne National Laboratorys Center for Nanoscale Materials, the researchers employed TEM to image the 2D materials crystal structure and chemical composition.

The researchers found that the graphene-zinc-oxide system becomes weakly magnetic with a 5-6 percentconcentration of cobalt atoms. Increasing the concentration of cobalt atoms to about 12 percentresults in a very strong magnet.

To their surprise, a concentration of cobalt atoms exceeding 15 percentshifts the 2D magnet into an exotic quantum state of frustration, whereby different magnetic states within the 2D system are in competition with each other.

And unlike previous 2D magnets, which lose their magnetism at room temperature or above, the researchers found that the new 2D magnet not only works at room temperature but also at 100 degrees Celsius (212 degrees Fahrenheit).

Our 2D magnetic system shows a distinct mechanism compared to previous 2D magnets, said Chen. And we think this unique mechanism is due to the free electrons in zinc oxide.

When you command your computer to save a file, that information is stored as a series of ones and zeroes in the computers magnetic memory, such as the magnetic hard drive or a flash memory.

And like all magnets, magnetic memory devices contain microscopic magnets with two poles north and south, the orientations of which follow the direction of an external magnetic field. Data is written or encoded when these tiny magnets are flipped to the desired directions.

According to Chen, zinc oxides free electrons could act as an intermediary that ensures the magnetic cobalt atoms in the new 2D device continue pointing in the same direction and thus stay magnetic even when the host, in this case the semiconductor zinc oxide, is a nonmagnetic material.

Free electrons are constituents of electric currents. They move in the same direction to conduct electricity, Yao added, comparing the movement of free electrons in metals and semiconductors to the flow of water molecules in a stream of water.

The new material which can be bent into almost any shape without breaking, and is a million times thinner than a sheet of paper could help advance the application of spin electronics or spintronics, a new technology that uses the orientation of an electrons spin rather than its charge to encode data. Our 2D magnet may enable the formation of ultra-compact spintronic devices to engineer the spins of the electrons, Chen said.

I believe that the discovery of this new, robust, truly two-dimensional magnet at room temperature is a genuine breakthrough, said co-author Robert Birgeneau, a faculty senior scientist in Berkeley Labs Materials Sciences Division and professor of physics at UC Berkeley who co-led the study.

Our results are even better than what we expected, which is really exciting. Most of the time in science, experiments can be very challenging, Yao said. But when you finally realize something new, its always very fulfilling.

Co-authors on the paper include researchers from Berkeley Lab, including Alpha NDiaye and Padraic Shafer of the Advanced Light Source; UC Berkeley; UC Riverside; Argonne National Laboratory; and Nanjing University and the University of Electronic Science and Technology of China.

The Advanced Light Source and Molecular Foundry are DOE national user facilities at Berkeley Lab.

The Stanford Synchrotron Radiation Lightsource is a DOE national user facility at SLAC National Accelerator Laboratory.

The Center for Nanoscale Materials is a DOE national user facility at Argonne National Laboratory.

This work was funded by the DOE Office of Science, the Intel Corporation, and the Bakar Fellows Program at UC Berkeley.

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News Scientists create the world's thinnest magnet - University of California