Spintronic devices utilize spin textures generated by quantum-physical interactions to revolutionize the field of electronics. A recent collaboration between Spanish and German researchers at BESSY II has delved into the study of graphene-cobalt-iridium heterostructures, unveiling a promising future for spintronics. The research showcases how two crucial quantum effects harmonize within these heterostructures, paving the way for cutting-edge spintronic devices based on these materials.
Spintronics harnesses the spins of electrons to execute logic operations and store information, offering the potential for faster and more energy-efficient operations compared to traditional semiconductor devices. However, creating and controlling spin textures in materials remains a challenge.
Graphene: A Spintronics Marvel
Graphene, a two-dimensional carbon structure, emerges as a key contender for spintronic applications. When graphene is paired with a thin film of a heavy metal, a robust spin-orbit coupling develops at their interface. This coupling engenders various quantum effects, including the Rashba effect and Dzyaloshinskii-Moriya interaction, crucial for stabilizing spin textures like skyrmions, ideal for spintronics.
Introducing Cobalt Monolayers
The research team has shown that the desired quantum effects are amplified when a few monolayers of cobalt, a ferromagnetic element, are interposed between graphene and the heavy metal, iridium. The samples grown on insulating substrates lay the groundwork for multifunctional spintronic devices leveraging these effects.
Revealing Interactions
‘At BESSY II, we scrutinized the electronic structures at the interfaces of graphene, cobalt, and iridium,’ says Dr. Jaime Sánchez-Barriga from HZB. Surprisingly, graphene not only interacts with cobalt but also, via cobalt, with iridium. The ferromagnetic cobalt layer enhances energy level splitting, influencing the spin-canting effect. ‘The number of cobalt monolayers dictates the extent of spin canting; three monolayers yield optimal results,’ adds Sanchez-Barriga.
Experimental data corroborates the findings, complemented by density functional theory calculations. The synergistic reinforcement of both quantum effects signifies a pioneering discovery.
Advancing Technology at BESSY II
Thanks to the sophisticated Spin-ARPES instruments at BESSY II, the researchers gained profound insights into the origin and precision of spin canting, surpassing previous capabilities. Prof. Oliver Rader, head of HZB’s “Spin and Topology in Quantum Materials” department, underscores the significance of these findings for the future of spintronics. The study unveils the immense potential of graphene-based heterostructures for the upcoming generation of spintronic devices.