Researchers have discovered a new type of magnetism in 2D materials that can help store data.
The team led by researchers from the University of Stuttgart experimentally demonstrated the previously unknown form of magnetism in atomically thin material layers.
Researchers revealed that the discovery is highly relevant for future magnetic data storage technologies and advances the fundamental understanding of magnetic interactions in two-dimensional systems.
“As data volumes continue to grow, future magnetic storage media must be able to store information reliably at ever higher densities,” says Professor Jörg Wrachtrup, Head of the Center for Applied Quantum Technologies (ZAQuant) at the University of Stuttgart, whose group led the project.
“Our results are therefore directly relevant for next-generation data storage technologies. At the same time, they are of fundamental importance, as they provide new insights into magnetic interactions in atomically thin materials.”
The team discovered the new magnetic state that emerges in a system consisting of four atomic layers of chromium iodide.
Researchers can selectively control this magnetism
“We can selectively control this magnetism by tuning the interactions between electrons in the individual layers,” explained Dr. Ruoming Peng, a postdoctoral researcher at the 3rd Physics Institute of the University of Stuttgart, who carried out the experiments at ZAQuant together with doctoral researcher King Cho Wong. “What is particularly remarkable is that the observed magnetic properties are robust against environmental perturbations.”
The chromium iodide investigated in the study belongs to the class of two-dimensional (2D) materials — systems composed of only a few atomic layers arranged in a crystalline lattice. It has long been known that 2D materials can exhibit properties that differ fundamentally from those of their three-dimensional bulk counterparts, according to a press release.
By slightly twisting two bilayers of chromium iodide with respect to each other, the Stuttgart researchers created a novel magnetic state. “In contrast, an untwisted bilayer does not exhibit a net external magnetic field, as shown in earlier studies,” says Peng. The twisting gives rise to so-called skyrmions — nanoscale, topologically protected magnetic structures that are among the smallest and most stable information carriers known in magnetic systems. For the first time, the team succeeded in creating and directly detecting skyrmions in a twisted two-dimensional magnetic material.
Published in Nature Nanotechnology journal, the research observed long-range magnetic textures extending beyond the single moiré unit cell, which we dub a super-moiré magnetic state. At small twist angles, the size of the spontaneous magnetic texture increases with twist angle, opposite to the underlying moiré wavelength. The spin-texture size reaches a maximum of about 300 nm in 1.1° twisted devices, an order of magnitude larger than the underlying moiré wavelength, and vanishes at twist angles above 2°, as per the study.