The one-atom thin 2D magnet, created by Dr. Jie Yao from the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, and his colleagues, could make big advances in next-generation memories, computing, spintronics, and quantum physics.
“We’re the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions,” Dr. Yao said.
“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,” added Rui Chen, a graduate student at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory.
Dr. Yao, Chen and their co-authors synthesized the 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 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, 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. It’s potentially scalable for mass production at lower costs,” Dr. Yao said.
To confirm that the resulting 2D film is just one atom thick, the researchers conducted scanning electron microscopy experiments to identify the material’s morphology, and transmission electron microscopy imaging to probe the material atom by atom.
With proof in hand that their 2D material really is just an atom thick, they demonstrated that the magnet successfully operates at room temperature.
As a whole, the experiments showed that the graphene-zinc-oxide system becomes weakly magnetic with a 5-6% concentration of cobalt atoms.
Increasing the concentration of cobalt atoms to about 12% results in a very strong magnet.
To the team’s surprise, a concentration of cobalt atoms exceeding 15% shifts 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 scientists found that the new 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. And we think this unique mechanism is due to the free electrons in zinc oxide,” Chen said.
The team’s work was published in the journal Nature Communications.
R. Chen et al. 2021. Tunable room-temperature ferromagnetism in Co-doped two-dimensional van der Waals ZnO. Nat Commun 12, 3952; doi: 10.1038/s41467-021-24247-w
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