Physicists create the first two-dimensional ferrimagnetism in graphene

Physicists create the first two-dimensional ferrimagnetism in graphene

St. Petersburg University physicists create the first two-dimensional ferrimagnetism in graphene

Graphic diagram illustrating the Hall effect in the studied system. 1 credit: SPbU

Scientists from St. Petersburg University and their foreign colleagues created the world’s first two-dimensional ferromagnetism in graphene. The use of the magnetic state obtained from graphene can become the basis of a new approach to electronics, increasing its energy efficiency and speed when developing devices using alternative technologies without the use of silicon.

Graphene, a two-dimensional modification of carbon, is the lightest and strongest of all two-dimensional materials available today, and is also highly conductive. In 2018, researchers from the University of Saint Petersburg, together with their colleagues from Tomsk State University and German and Spanish scientists were the first in the world to modify graphene and give it the properties of cobalt and gold – magnetism and spin-orbit interaction (between the moving electron in graphene and its own magnetic moment). When interacting with cobalt and gold, graphene not only retains its unique characteristics, but also partially takes on the properties of these metals.

As part of this new work, the scientists synthesized a system with a ferrimagnetic state of graphene. It is a unique state in which the substance has magnetization in the absence of an external magnetic field. The physicists used a similar substrate consisting of a thin layer of cobalt and a gold alloy on its surface.

During surface alloying, dislocation loops formed under the graphene. These loops are triangular regions with a lower density of cobalt atoms which the gold atoms have come closer to. Until now, it was known that single-layer graphene could only be fully magnetized uniformly. However, studies by scientists from the University of Saint Petersburg have shown that it is possible to control the magnetization of individual sublattice atoms by selective interaction with structural defects in the substrate.

“This is an important finding, as all electronic devices use electrical charges and involve generation of heat when current flows. Our research will eventually allow information to be transmitted in the form of spin currents. is about a new generation of electronics, a fundamentally different logic and a new approach to technology development that reduces power consumption and increases the speed of information transfer,” explained Artem Rybkin, Principal Investigator of the Research, Senior Research Associate at the Laboratory of Electronic and Spin Structure of Nanosystems at St. Petersburg University.

The second important feature of graphene synthesized by physicists at St. Petersburg University is the strong spin-orbit interaction. In this structure, the reinforcement of this interaction is explained by the presence of gold atoms under the graphene. At a certain ratio of magnetic parameters and spin-orbit interaction, it is possible to go from the trivial, that is to say familiar, state of graphene to a new topological state.

Research results are published in Physical examination letters.

More information:
Artem G. Rybkin et al, Sublattice Ferrimagnetism in Quasi-Autonomous Graphene, Physical examination letters (2022). DOI: 10.1103/PhysRevLett.129.226401

Provided by Saint Petersburg State University

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