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Monday Oct 03, 2022

Unique Quantum Material Could Allow For Incredible Powerful, Ultra-Compact Computing

Information is transferred through semiconductors using electron movement and stored in magnetic materials in the direction of the electron spin. To shrink devices while improving their performance–a goal of an emerging field called spin-electronics (“spintronics”)–researchers are searching for unique materials that combine both quantum properties. A Columbia University team of chemists, physicists and scientists discovered a strong link between electron transportation and magnetism in chromium sulfur bromide (CrSBr) and published it in the journal Nature Materials.

CrSBr was created in the laboratory of Chemist Xavier Roy. It is a van der Waals crystal, which can be broken into stackable 2D layers, each one atom thin. CrSBr crystals can be maintained at ambient temperatures, unlike other related materials which are easily destroyed by water and oxygen. These crystals retain their magnetic properties even at a relatively high temperature (-280F), which means they can be used without expensive liquid Helium that has to be cooled down to -450F.

The crystallization of chromium sulfidebromide into thin layers can be separated and stacked to make nanoscale devices. Columbia researchers discovered that the material’s magnetic and electronic properties were linked together. This discovery could be used for fundamental research as well potential spintronics applications. Credit: Yimei Zhu and Myung-Geun Han

Evan Telford, a postdoctoral researcher in the Roy lab, said that CrSBr is infinitely more easy to work with than 2D magnets. This allows us to fabricate new devices and test their properties. He graduated in 2020 with a PhD from Columbia in Physics. Nathan Wilson, Xiaodong Xu and Xiaoyang Zhu from Columbia discovered a linkbetween magnetisms and the way CrSBr reacts to light last year. Telford was the leader of the effort to discover its electronic properties in the current research.

The team used an electric field to study CrSBr layers across different electron densities, magnetic fields, and temperatures–different parameters that can be adjusted to produce different effects in a material. The magnetic properties of CrSBr also changed as did their electronic properties.

“Semiconductors possess tunable electronic characteristics. Magnets can have tunable spin configurations. Roy said that CrSBr has both knobs. This makes CrSBr appealing for fundamental research as well as potential spintronics applications.”

It is difficult to measure magnetism directly because of shrinkage in the material, said Telford. However, it is possible to measure electrons’ movement with a parameter called resistance. Resistance can be used in CrSBr to indicate otherwise invisible magnetic states. Roy said, “That’s very strong,” especially since researchers are looking to build chips from 2D magnets in the future. This could be used to do quantum computing or to store large amounts of data in small spaces.

Telford said that the link between the material’s magnetic and electronic properties was caused by defects in the layers. This was a fortunate break for the team. People want the best material. He said that although our crystals were imperfect, this wouldn’t have been possible without them.

The Roy lab is now exploring ways to make van der Waals crystals that can be peelable. This will allow the Roy lab to better tune the material’s properties. They also explore whether different combinations could work at higher temperatures and still retain their valuable combined properties.

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