Adapted from this Berkeley Lab news release.
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 ultrathin magnet, which was recently reported in the journal Nature Communications, could make big advances in next-gen memory devices, computing, spintronics, and quantum physics.
“We’re the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions,” said Foundry user and senior author Jie Yao, a faculty scientist in Berkeley Lab’s Materials Sciences Division and associate professor of materials science and engineering at UC Berkeley.
The magnetic component of today’s 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.
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.
To confirm that the resulting 2D film is just one atom thick, Yao and his team conducted scanning electron microscopy experiments at the Foundry to identify the material’s morphology, and transmission electron microscopy (TEM) imaging to probe the material atom by atom.
The researchers found 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 their 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.
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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).
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 electron’s spin rather than its charge to encode data.