Twist physics is a new area of ​​quantum physics that explores new quantum phenomena by stacking van der Waals materials. Purdue University researchers have advanced the field by introducing quantum spin into the twisted double-layer material of an antiferromagnet, creating tunable moiré magnetism. This breakthrough proposes new materials for spintronics and is expected to advance the development of memory and spin logic devices.

Purdue University quantum researchers have demonstrated tunable moiré magnetism by twisting a double-layer film of an antiferromagnet. Twist technique isn't a new dance move, fitness equipment, or new music fad, it's much cooler than any of that. It is an exciting new development in the fields of quantum physics and materials science. Van der Waals materials are stacked on top of each other in layers, just like a roll of paper, and can be easily twisted and rotated while remaining flat. Quantum physicists use these stacks to discover interesting quantum phenomena.

Quantum physicists have used these stacks to discover interesting quantum phenomena. Combining the concept of quantum spin with twisted double-layer stacks of antiferromagnets, it is possible to create tunable moiré magnetism. This provides a new class of material platform for spintronics, the next step in dual electronics. This new science may lead to promising memories and spin logic devices, opening up a new path for spintronics applications in the physics community.

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

A quantum physics and materials research team at Purdue University used the interlayer antiferromagnetic coupling van der Waals (vdW) material CrI3 as a medium to introduce twisting technology to control the spin degree of freedom. They published their research results titled "Electrically Tunable Moiré Magnetism in Twisted Chromium Triiodide Bilayers" in Nature Electronics.

"In this study, we created twisted double-bilayer chromium trioxide, that is, there is a twist angle between the double-layer and the double-layer," said Dr. Guanghui Cheng, co-first author of the paper. "We report moiré magnetism with rich magnetic phases and achieve remarkable tunability through electrical methods."

Molar superlattice structure of twisted double bilayer (tDB) CrI3 and its magnetic behavior detected by the magneto-optical-Kerr effect (MOKE). Part a of the figure above shows a schematic diagram of a Moiré superlattice fabricated by interlayer twisting. Bottom: Non-collinear magnetic states can occur. The MOKE results shown in part b of the figure above show that compared to the antiferromagnetic order in natural antiferromagnetic double-layer CrI3, there are both antiferromagnetic (AFM) and ferromagnetic (FM) orders in "molar magnetic" tDBCrI3. Image source: Illustration: GuanghuiCheng and YongP.Chen

"We stacked and twisted an antiferromagnet onto itself, and we got a ferromagnet," Cheng said. "It is also a striking example of the recent emergence of 'twisted' or moiré magnetism in twisted 2D materials, where the angle of twist between two layers of material provides a powerful tuning knob that dramatically changes the material's properties."

"To make the twisted bilayer CrI3, we used what's called a tear-and-stack technique, where one part of the bilayer CrI3 is ripped apart, rotated and stacked onto another part," Cheng explains. "Through magneto-optical Kerr effect (MOKE) measurements, we observed the coexistence of ferromagnetic and antiferromagnetic orders, a hallmark of Moiré magnetism, and further demonstrated voltage-assisted magnetic switching. This Moiré magnetism is a new form of magnetism with spatially varying ferromagnetic and antiferromagnetic phases that alternate periodically according to a Moiré superlattice."

To date, twisted electronics has mainly focused on modulating electronic properties, such as twisted bilayer graphene. The Purdue team wanted to introduce twist into the spin degree of freedom and chose to use the interlayer antiferromagnetic coupling vdW material CrI3. By making samples with different twist angles, it is possible to stack antiferromagnets twisting into themselves. In other words, once fabrication is complete, the twist angle of each device is fixed before MOKE measurements are performed.

Upadhyaya and his team performed theoretical calculations on the experiment. This provides strong support for the observation results of Dr. Cheng's team. He said: "Our theoretical calculations revealed a rich phase diagram, including non-conjugated phases such as TA-1DW, TA-2DW, TS-2DW, TS-4DW, etc."

This study coincides with an ongoing study by Cheng's team. Prior to this work, the team had recently published several papers related to new physics and properties of "two-dimensional magnets," such as "Emergence of electric-field-tunable interfacial ferromagnetismin2Dantiferromagnetheterostructures" recently published in Nature Communications. This research direction holds exciting possibilities in the fields of dual electronics and spintronics.

"The discovered Moliere magnets provide a new class of materials platform for spintronics and magnetoelectronics," Cheng said. "The observed voltage-assisted magnetic switching and magnetoelectric effects may lead to promising memory and spin logic devices. As a new degree of freedom, twisting can be applied to various homo/different layers of vdW magnets, opening up opportunities to pursue new physics as well as spintronics applications."

Compiled source: ScitechDaily