Manufacturing Bits: Aug. 3

World’s thinnest magnet; Kondo insulators.


World’s thinnest magnet
Lawrence Berkeley National Laboratory, the University of California at Berkeley and others have developed what researchers say is the world’s thinnest magnet.

The one-atom-thin, two-dimensional (2D) magnet could one day pave the way towards new spin electronics or spintronics memory devices and other technologies in the market. Spintronics uses the orientation of an electron spin rather than a charge to encode data.

2D magnetic materials are promising. These materials enable exceptional spintronic capabilities. These capabilities are key for the development of next-generation memory and electronic devices.

For decades, the industry has attempted to develop thinner and smaller 2D magnets. The problem? 2D magnets tend to lose their magnetism and become unstable at room temperature.

To overcome these problems, the industry is developing 2D magnets based on diluted magnetic oxides (DMOs) materials. Levering the properties of DMOs, Berkeley Lab and UC Berkeley synthesized a new 2D magnet. The magnet, called a cobalt-doped van der Waals zinc-oxide magnet, is synthesized from a solution of graphene oxide, zinc and cobalt.

The magnet consists of a single atomic layer of zinc-oxide with a smattering of cobalt atoms, which are sandwiched between layers of graphene. The new material, which can be bent into almost any shape without breaking, is a million times thinner than a sheet of paper. Researchers found that the new 2D magnet not only works at room temperature but also at 100 degrees Celsius.

To confirm that the resulting 2D film is one atom thick, researchers used scanning electron microscopy at Berkeley Labs to identify the material’s morphology. Transmission electron microscopy (TEM) imaging was used to probe the material atom by atom. X-ray experiments at Berkeley Lab’s Advanced Light Source characterized the 2D material.

“We’re the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions,” said Jie Yao, a faculty scientist in Berkeley Lab’s Materials Sciences Division and associate professor of materials science and engineering at UC Berkeley.

“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. 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: it’s as thin as a single atom,” Yao said. “It opens up every single atom for examination, which may reveal how quantum physics governs each single magnetic atom and the interactions between them.”

Kondo insulators
Using a powerful and giant magnet, researchers at the National High Magnetic Field Laboratory (National MagLab) at Los Alamos National Laboratory have revealed a new state of matter in Kondo insulators.

The University of Michigan, Kyoto University and Los Alamos conducted the research. Researchers studied the Kondo insulator ytterbium dodecaboride (YbB12) using the new 75-tesla duplex magnet housed at the National MagLab’s Pulsed Field Facility at Los Alamos. Using this magnet, researchers found an exotic new phase of matter at high magnetic fields.

MagLab develops several different types of large and powerful magnets. Dozens of measurement techniques can be performed at the MagLab’s user facilities. Tesla, or T, is the measurement of magnetic field strength. A refrigerator magnet has a field of 0.01 T. An MRI scanner has a 1.5 tesla magnet. A 32 T magnet is more than 3,000 times stronger than a refrigerator magnet, according to MagLab.

Meanwhile, researchers explored Kondo insulators using the new 75-tesla duplex magnet. “In Kondo insulators, there is an unusual quantum-mechanical mixing of mobile electrons and magnetic atoms, making these materials attractive as model systems for basic science, electronic devices, and possibly quantum computing,” according to MagLab. “Unlike simple metals and insulators, YbB12 exhibits properties of both — its electrical resistance behaves like that of an insulator, but it also clearly shows quantum oscillations at high magnetic fields that are a fundamental metallic property.”

“A plethora of theories has emerged to account for such behavior,” said John Singleton, a fellow at the MagLab’s Los Alamos campus. “Some physicists believe this is a condensed-matter incarnation of neutral Majorana fermions, entities normally explored in particle physics.”

In particle physics, a fermion is a particle that has a half odd integer spin. A Majorana fermion is a fermion that is its own antiparticle.

To test these theories, researchers used the new 75-tesla duplex magnet to suppress the insulating properties of YbB12. They measured the quantum oscillations and various properties affected by fermions.

“The extra 10 tesla above our standard pulsed magnets provided by the duplex magnet enabled this new state of matter — exotic fermions gradually being drowned in a sea of normal electrons — to be tracked across a wide range of magnetic fields for the first time,” said Singleton.

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