Berkeley Researchers Create Magnet as Thin as an Atom

Researchers from the Department of Material Science and Engineering at the University of California found that cobalt-doped zinc-oxide in a specific concentration could perform as a monolayer magnet. This would mean that a two-dimensional magnet can be stable at room temperature and does not lose its magnetic properties.

Thin magnets are used in digital data storage devices such as hard disks. The magnets in these devices act as a part of a sensor. A head that is able to detect magnetization moves very close to separate regions of the magnet. The detection of magnetization stores data as binomial numbers. The thickness of the magnetic layers affects the thickness of the magnetic regions, therefore, affecting the data storage density. As the magnet layers get thinner the density of data stored is higher.

“This discovery is exciting because it not only makes 2D magnetism possible at room temperature, but it also uncovers a new mechanism to realize 2D magnetic materials,” said Rui Chen a UC Berkeley graduate student in the Yao Research Group and one of the lead authors in this new research.

Illustration of magnetic coupling in a cobalt-doped zinc-oxide monolayer. Red, blue, and yellow spheres represent cobalt, oxygen, and zinc atoms, respectively. Image courtesy of Berkeley Lab

The 2D Magnet 

This is not the first project to successfully design a 2D magnet. But previous 2D magnets lose their magnetism with time. The newly designed magnet is magnetically stable at room temperature or higher.

To create the 2D magnet the researchers used a lab oven to transform a synthesized solution of graphene oxide, zinc, and cobalt into a single layer. After heating this mixture and forming a 2D layer, graphene must be removed or burned away in order to have a pure cobalt-doped zinc oxide layer.

 

Testing and Findings

The researchers used scanning electron microscopy (SEM) in order to test and ensure the two-dimensional property of the magnet. In other words, the SEM prevails that the magnet is 1 atom thick.

Also, the researchers conducted X-Ray testing to verify the electronic and crystal structures on the synthesized 2D magnets and to determine the magnetic properties at high temperatures.

The percentage of doping of cobalt turned out to be a specific number at 15%. If the concentration of cobalt is lower the magnet becomes weakly magnetic. Otherwise, if the concentration is above 15% the magnetic system will be disrupted by different magnetic states within the 2D magnet.

“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, it’s always very fulfilling.”

 

The Future of the Magnet

The researchers believe that this magnet will open a door to more studies in many fields in magnetism such as uncovering the mechanism to find new 2 dimensional magnetic materials and studying the relation between quantum physics and magnetic atoms.

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