Two-dimensional magnetic materials are listed as building blocks for the next generation of small, fast electronic devices. These materials, made from layers of crystal plates but several atoms thick, derive their unique magnetic properties from the internal needle-like rotations of their electrons. The atomic-scale tin of the blades means that this spin can be manipulated at very high scales by external electric fields, which can lead to a new low-energy data storage and information processing system. But knowing exactly how to design 2D materials with specific magnetic properties (layered 2D materials that can host unique magnetic fields) that can be precisely manipulated remains an obstacle to their application.
New materials with exotic magnetic functions can enable a new generation of small, fast electronic devices.
Now, as reported in the journal Science Advances, researchers at Lawrence Berkeley National Laboratory (Berkeley Lab), UC Berkeley, Cornell, and Rutgers University have discovered layered 2D materials that can host unique magnetic fields. parts that remain stable at room temperature and will therefore eventually be used in future everyday appliances. Atomic-scale images of the material show the exact chemical and structural properties that are responsible for these components and their strength. Berkeley Lab researchers have experience identifying unexpected magnetic properties in atomic thin layers of bulk crystals, many of which are based on semiconductor materials doped with metal atoms. UC Berkeley graduate student Tyler Reichanadter, the co-author of the study, calculated how the electronic structure of common 2D materials changes by exchanging different atoms, in this case, some iron for cobalt. This particular confusion will result in a crystal structure that cannot be placed in its mirror image and will lead to the possibility of exotic, vortex spin arrangements called skyrmions, which will be explored as building blocks for future low-energy calculations.
Study co-authors Hongrui Zhang, a postdoctoral researcher at UC Berkeley, and Xiang Chen, a postdoctoral researcher at Berkeley Lab and UC Berkeley, used crystal growth devices to explore some of the best 2D materials, including cobalt-doped iron and germanium telluride (Fe5GeTe2) in the form of nanoflowers. . Fe5GeTe2 is a typical 2D magnetic material due to its unique layered structure and crystal symmetry, with iron atoms occupying specific points in the crystal structure. They found that by replacing only half of the iron atoms with cobalt atoms – whose small difference in electronic configuration means that the atoms naturally occupy small different places in the crystal – they can spontaneously destroy the natural crystal symmetry of the material, which in turn changes its spin structure.
“It’s not easy. The synthesis of these structures takes days or months, and we’ve gone through hundreds of crystals,” said Chen, who specializes in synthesizing such complex materials.
Co-authors Sandhya Susarla, a postdoctoral fellow at Berkeley Lab, and Yu-Tsun Shao, a postdoctoral fellow researcher at Cornell, confirmed the atomic scale and electronic structure of complex materials using electron microscopy capabilities at the National Center for Electron Microscopy at Molecular Foundry.
“It’s pure science of discovery and completely unexpected,” said Ramamoorthy Ramesh, a chief material scientist at Berkeley Lab and chief correspondent for the author of the article. “The team tried to manipulate the electronic structure and found that by breaking the symmetry, the material could host skyrmions.”
Other Berkeley Lab authors on the paper include Robert Birgeneau, Jeff Neaton, Peter Fischer, Jie Yao, Kaichen Dong, and Rui Chen.
Zhang used magnetic force microscopy to visualize skyrmions over large areas of such crystals. By monitoring the development of skyrmions as a function of temperature and magnetic field, the researchers determined the physical conditions that led to their stability. In addition, by sending an electric current through the material, the researchers found that they could cause skyrmions to move in the material independently of the atoms that lead to their formation.
Finally, David Raftrey, a Berkeley Lab researcher and UC Santa Cruz graduate student, performed a micromagnetic simulation to interpret the observed electronic pattern of materials. Because layered materials can have many thicknesses at room temperature and above, scientists believe that their magnetic properties can be improved and expanded. “We are interested in microelectronics, but basic questions about the physics of materials really inspire us,” Zhang said.
