The magnetic moment of electrons (spin) is used in spintronics to manipulate and transfer information. A 2D, compact spin-logic circuitry could be made from 2D materials. These materials can carry the spin information long distances and provide intense spin polarization. The University of Groningen (The Netherlands), and Columbia University (USA), have shown that magnetic Graphene is the best choice for 2D spin-logic devices. It efficiently converts the charge into spin current and can transfer this strong, long-range spin-polarization. This discovery will be published in Nature Nanotechnology today, May 6, 2021.
The spintronic devices promise energy-saving and high-speed alternatives to current electronics. These devices use electrons’ magnetic moment (or spins) to store and transfer information. It is looking for smaller spintronic devices to keep memory technology at a lower level. This means they are actively seeking out atomically thin materials that can generate significant spin signals and transmit spin information over long distances of micrometers.
Graphene
Graphene has been the 2D material most suitable for transporting spin information for over a decade. However, Graphene can’t generate spin current by its properties unless they are modified. This can be achieved by making Graphene magnetic. Because magnetism favors one type of spin, it would cause an imbalance in the numbers of electrons with spin up and spin down. This would create a high-spin-polarized current in magnetic Graphene.
The Physics of Nanodevices group experimentally confirmed this idea, led by Prof. Bart van Wees from the University of Groningen’s Zernike institute of advanced materials. They could directly measure the large spin-polarization generated by magnetic Graphene when they placed Graphene close to CrSBr (2D layered antiferromagnet).
Spin-logic
For injecting and sensing the spin signal into Graphene in conventional graphene-based spinning devices, cobalt (ferromagnetic) electrodes are used. Talieh Ghiasi is the first author of this paper. In contrast, circuits made from magnetic Graphene can inject, transport, and detect spins. “We saw an extremely large spin-polarization in conductivity of 14% within the magnetic Graphene. This, along with Graphene’s exceptional charge and spin transport characteristics, allows for the realization of all-graphene 2D spinning logic circuitries, where only the magnetic Graphene can inject, transport, and detect the spin information.
These spintronic devices also take advantage of the inevitable heat dissipation in electronic circuitry. “We observed that the temperature gradient of magnetic Graphene caused by Joule heating can be converted to spin current. Ghiasi says this happens due to the spin-dependent Seebeck phenomenon, also observed in Graphene in our experiments. Magnetic Graphene’s efficient thermal and electrical generation of spin currents promises significant advances in 2D and 3D spintronic and spincaloritronic technologies.
Graphene Flagship
The magnetic behavior of the outermost layer of the nearest antiferromagnet is also a factor in the spin transport in Graphene. These spin transport measurements allow for the size of the magnetization of one atomic layer. The magnetic graphene-based devices address the technologically most relevant aspects of magnetism for Graphene’s 2D memory and sensory system and offer further insight into the physics behind the appeal.
These results will be examined in the context of the EU Graphene Flagship, which works towards new uses of graphene 2D materials.