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 memories, computing, spintronics, and quantum physics.
It was discovered by scientists at the Department of Energy's Lawrence Berkeley National Laboratory
and UC Berkeley.
The researcher said that they are the first to make a room-temperature 2D magnet that
is chemically stable under ambient conditions.
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.
The magnetic component of today's memory devices is typically made of magnetic thin films.
But at the atomic level, these magnetic films 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.
The researcher says that their 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: It's 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.
With a conventional bulk magnet where most of the magnetic atoms are deeply buried inside
the material, such studies would be quite challenging to do.
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, graphene is burned away, leaving behind just a single atomic layer
of cobalt-doped zinc-oxide.
It's potentially scalable for mass production at lower costs.
To confirm that the resulting 2D film is just one atom thick, the research team conducted
scanning electron microscopy experiments at Berkeley Lab's Molecular Foundry 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, the researchers
went on to the next challenge that had confounded researchers for years: Demonstrating a 2D
magnet that successfully operates at room temperature.
X-ray experiments at Berkeley Lab's Advanced Light Source characterized the 2D material's
magnetic parameters under high temperature.
Additional X-ray experiments at SLAC National Accelerator Laboratory's Stanford Synchrotron
Radiation Lightsource verified the electronic and crystal structures of the synthesized
2D magnets.
And at Argonne National Laboratory's Center for Nanoscale Materials, the researchers imaged
the 2D material's crystal structure and chemical composition using transmission electron microscopy.
As a whole, the research team's lab 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 researchers' 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 researchers found that the new 2D magnet not only works at room temperature but also
at 100 degrees Celsius
When you command your computer to save a file, that information is stored as a series of
ones and zeroes in the computer's 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.
Zinc oxide's 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.
The researchers say that new material - which can be bent into almost any shape without
breaking, and is 1 millionth the thickness of a single 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.