2D graphene spin valve leverages van der Waals magnet proximity for efficient spintronics

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Graphene, particularly in its purest form, has long been considered a promising material for developing spintronic devices. These devices leverage the intrinsic angular momentum (i.e., spin), as opposed to the charge, of electrons to transmit and process data.

A proposed approach to generate and detect spins relies on the proximity of graphene to a nearby material that can alter its properties. So far, however, the successful development of spintronics utilizing this approach alone has proved highly challenging.

Researchers at CIC nanoGUNE BRTA and other institutes recently realized a spintronic device that leverages proximity effects alone, specifically a 2D graphene-based spin valve. The functioning of this valve, introduced in a paper published in Nature Electronics, relies only on the proximity to the van der Waals magnet Cr₂Ge₂Te_6.

"The field of spintronics has evolved significantly since the pioneering discoveries of spin injection and giant magnetoresistance in the 1980s," Haozhe Yang, first author of the paper, told Phys.org.

"These discoveries, which relied on spin-polarized electron injection in a 3D structure from a ferromagnetic metal to a normal metal, earned Albert Fert and Peter Grünberg the 2007 Nobel Prize in Physics. Their groundbreaking achievements laid the foundation for ongoing research into complex material combinations and interface optimization techniques."

The primary objective of this recent study by Yang and his colleagues was to tackle a long-standing research challenge, namely that of realizing the first-ever seamless 2D spintronic device. The spin valve they developed could enable the manipulation and transport of spin entirely in the 2D plane.

"We constructed a spin valve entirely from proximitized structures," explained Yang. "This device consists of a single piece of graphene, locally functionalized by the proximity effect using the van der Waals magnetic insulator Cr₂Ge₂Te₆. Two functionalized graphene regions act as the spin injector and detector, while the pristine section in between serves as the spin transport channel."

The spin valve introduced by the researchers has a key advance over previous designs, namely the lack of physical interfaces between its components. The absence of these interfaces can reduce the loss of spins, improving the device's performance.

"Our experiments revealed that proximitized graphene, the central component of this all-2D spin valve, exhibits a coexistence of spin-orbit and magnetic proximity effects," said Yang. "This seamless structure strongly demonstrates the feasibility of using the proximity effect to develop essential electronic devices."

In initial tests, the team's 2D graphene spin valve attained very promising results, exhibiting spin-orbit and magnetic exchange coupling simultaneously, which contributed to a sizeable anomalous Hall effect. This recent study could soon pave the way for developing a new kind of highly efficient spintronic device, which the team refers to as "proximitronics."

"We believe this simple yet innovative all-proximitized spintronic device will inspire further research into the fundamental mechanisms and applications of the proximity effect," added Yang.

"Its significance could extend beyond spintronics, potentially forming the basis for a new research field. Our immediate goal is to deepen the understanding of proximitized systems and explore their integration into advanced electronic and spintronic applications."

More information: Haozhe Yang et al, A seamless graphene spin valve based on proximity to van der Waals magnet Cr₂Ge₂Te₆, Nature Electronics (2024). DOI: 10.1038/s41928-024-01267-0.

Journal information: Nature Electronics

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