The information in computers is transmitted by semiconductors through electrons and is stored in the form of electron spin on magnetic objects. To reduce devices while improving their performance — the goal of an emerging field called spin-electronics (“spintronics”) – researchers are looking for unique materials that combine both quantum features. Writing in Nature, a team of Columbia physicists finds a strong link between electron transport and magnetism in a substance called chromium sulfide bromide (CrSBr).
Created in the Chemist Xavier Roy Lab, CrSBr is a van der Waals crystal that can be processed into 2D layers of just a few thin atoms. Unlike related substances rapidly degraded by oxygen and water, CrSbr crystals are stable in local conditions. These crystals also retain their magnetic properties at a temperature of about 280F, avoiding the need for an expensive helium cooler at 450F temperatures,
“CrSBr is much easier to work with than other 2D magnets, which allows us to innovate and explore their properties,” said Evan Telford, a postdoc lab in Roy who received a Ph.D. in physics from Columbia in 2020. Last year, colleagues Nathan Wilson and Xiaodong Xu at the University of Washington and Xiaoyang Zhu in Columbia discovered the connection between magnetism and how CrSBr reacts to light. Telford has led an effort to test its electronic properties in the current work.
The team used the electric field to study CrSBr layers across a wide range of electron density, magnetic fields, and temperatures — different parameters can be adjusted to produce different results. As the electronic structures in CrSBr change, so does its magnetism.
“Semiconductors have reusable electronic components. Magnets have a flexible spin configuration. At CrSBr, these two knots are combined,” Roy said. “That makes CrSBr attractive in both basic research and a potential application for spintronics.”
Magnetism is challenging to measure directly, especially as the size of the material decreases, explains Telford, but it is easier to estimate how electrons move with a parameter called resistance. At CrSBr, resistance can act as a representative of invisible magnetic fields. “That’s very powerful,” Roy said, “especially as researchers look to one day create chips with these 2D magnets, which can be used for quantum computing and keeping large amounts of data in a small space.
Telford said that the connection between the electrical appliances and the magnet was due to a layer-team disability, a lucky break. “People tend to want things as ‘clean’ as possible. Our crystals were flawed, but otherwise, we would not have seen this combination,” he said.
From here, Roy’s laboratory experiments with deliberately magnifying van der Waals crystals with deliberate defects to improve the ability to fine-tune the material elements. They also examine whether different substances can operate at higher temperatures while combining those crucial properties.