The Quantum Revolution: Combining Spintronics and Spintronics to Enable Advanced Electronics

Purdue University quantum researchers twist a double layer of an antiferromagnet to demonstrate tunable Moiré magnetism.

Twistronics are not a new dance move, fitness equipment, or new musical fad. No, it’s much cooler than either one. This is an exciting new development in quantum physics and materials science, in which van der Waals materials stack up in layers, like reams of paper, and can be easily twisted and rotated while remaining flat, and quantum physicists have already used these materials Stack up to discover interesting quantum phenomena.

Combining the concept of quantum spin with the twisted double-bilayer of antiferromagnets, it is possible to obtain tunable Mohr magnetism. This suggests a new materials platform for the next step in dual electronics: spintronics. This new science may lead to promising memories and spin logic devices, opening up a new path for the physical world through spintronic applications.

By twisting a van der Waals magnet, non-collinear magnetic states can emerge with significant electrical tunability.Image credit: Ryan Allen, Second Bay Studios

A team of Purdue quantum physics and materials researchers uses CrI to introduce a twist to control spin degrees of freedom₃, an interlayer antiferromagnetic coupled van der Waals (vdW) material as its medium. They published their results, “Electrically tunable Moiré magnetism in chromium triiodide twisted bilayers,” natural electronics.

“In this study, we created twisted double bilayer CrI₃, that is, double layer plus double layer, with a twist angle between them,” said Dr. Cheng Guanghui, co-lead author of the publication. “We electrically report Moiré magnetism with rich magnetic phases and remarkable tunability.”

Moiré superlattice structure of twisted double bilayer (tDB) CrI3 and its magnetic behavior probed through the magneto-optical Kerr effect (MOKE). Part a above shows a schematic of a Moiré superlattice fabricated through interlayer twisting. Bottom panel: Non-collinear magnetic states may occur. Part b above shows MOKE results showing the coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) levels in the “Moire magnet” tDB CrI3, compared to the AFM level in natural antiferromagnetic double layer CrI3.Image source: Illustration by Guanghui Cheng and Yong P. Chen

“We stacked the antiferromagnet and twisted it onto itself, and voila, we got a ferromagnet,” Chen said. “This is also a striking example of the recent emergence of ‘twisted’ or moiré magnetic regions in twisted 2D materials, where the twist angle between two layers provides a powerful tuning knob and dramatically changes the material properties. “

“Creating twisted double-layer CrI₃we tear off part of the double-layer CrI₃, rotated and stacked onto another piece using what’s called a tear-and-stack technique,” ​​Cheng explains. “Through measurements of the magneto-optical Kerr effect (MOKE), a sensitive tool for probing magnetic behavior down to a few atomic layers, we observed the coexistence of ferromagnetic and antiferromagnetic order, which is the property of Mohr magnetism. “

So far, bielectronics has mainly focused on modulating electronic properties, such as twisting double layers Graphene. Purdue team wanted to introduce torsional rotational freedom and chose to use CrI₃, an interlayer antiferromagnetic coupling vdW material. By manufacturing samples with different twist angles, the result of stacked antiferromagnets twisting themselves can be achieved. In other words, once fabrication is complete, the twist angle of each device is fixed and MOKE measurements are then taken.

Upadhyaya and his team performed theoretical calculations for this experiment. This provides strong support for Chen’s team’s observations.

“Our theoretical calculations reveal rich phase diagrams with non-collinear phases for TA-1DW, TA-2DW, TS-2DW, TS-4DW, etc.,” Upadhyaya said.

This study feeds into ongoing research by Chen’s team.This work follows several recent publications by the team related to novel physics and properties of “two-dimensional magnets,” such as “The emergence of electric field-tunable interfacial ferromagnetism in two-dimensional antiferromagnetic heterostructures.” , the article was recently published in nature communications. This research avenue holds exciting possibilities in the fields of bispintronics and spintronics.

“The discovered Moiré magnet provides a new materials platform for spintronics and magnetic electronics,” Chen said. “The observed voltage-assisted magnetic switching and magnetoelectric effects may lead to promising memory and spin logic devices. As a novel degree of freedom, twisting can be applied to homogeneous/heterogeneous duals of various vdW magnets. layers, providing opportunities to pursue new physics and spintronics applications.”

Reference: “Electrically Tunable Moiré Magnetism in Chromium Triiodide Twisted Bilayers” by Guanghui Cheng, Mohammad Mushfiqur Rahman, Andres Llacsauanga Allcca, Avinash Rustagi, Xingtao Liu, Lina Liu, Lei Fu, Yanglin Zhu, Zhiqiang Mao, Kenji Watanabe, Takashi Taniguchi, Pramey Upadhyaya and Yong P. Chen, June 19, 2023 natural electronics.
DOI: 10.1038/s41928-023-00978-0

The team, primarily from Purdue University, has two equally contributing lead authors: Dr. Guanghui Cheng and Mohammad Mushfiqur Rahman. Cheng was a postdoc in Dr. Yong P. Chen’s group at Purdue University and is now an assistant professor at Northeastern University’s Advanced Materials Research Institute (AIMR, where Chen is also a principal investigator). Mohammad Mushfiqur Rahman is a PhD student in Dr. Pramey Upadhyaya’s group. Chen and Upadhyaya are both corresponding authors of the publication and are both professors at Purdue University. Chen is the Karlak-Horowitz Professor of Physics and Astronomy, Professor of Electrical and Computer Engineering, and Director of the Institute for Quantum Science and Engineering at Purdue University. Upadhyaya is an assistant professor of electrical and computer engineering. Other members of the Purdue University-affiliated team include Andres Llacsauanga Allcca (doctoral student), Dr. Lina Liu (postdoctoral fellow) and Dr. Lei Fu (postdoctoral fellow) in Professor Chen’s thematic group, Dr. Avinash Rustagi (postdoctoral fellow) and Dr. Liu Xingtao (bomber) in Upadhyaya’s thematic group. Former research assistant at the KNEM Technology Center).

This work was supported by the U.S. Department of Energy (DOE) Office of Science through the Quantum Science Center (QSC, National Quantum Information Science Research Center) and the Department of Defense (DOD) Multidisciplinary University Research Initiative (MURI) program (FA9550-20-1-0322 ). Cheng and Chen also received partial support from WPI-AIMR, JSPS KAKENHI Basic Science A (18H03858), New Science (18H04473 and 20H04623), and the Tohoku University FRiD program in the early stages of their research.

Upadhyaya also acknowledges support from the National Science Foundation (NSF) (ECCS-1810494).Bulk Chrome₃ The crystal was provided by Zhiqiang Mao’s research group at Penn State University with support from the U.S. Department of Energy (DE-SC0019068). Bulk hexagonal boron nitride crystals were provided by Kenji Watanabe and Takashi Taniguchi of the National Institute of Materials Science, Japan, with support from JSPS KAKENHI (grant numbers 20H00354, 21H05233, and 23H02052) and the World-Class International Research Center Program (WPI) of the Ministry of Education, Culture, Sports, Science and Technology of Japan. .