Researchers at Forschungszentrum Jülich, University of Duisburg-Essen, Max Planck Institute of Microstructure Physics, Johannes Kepler University Linz and University of California Davis have created the first experimentally verified two-dimensional half metal—a material that conducts electricity using electrons of just one spin type: either "spin-up" or "spin-down."
Their work could mark a milestone in the quest for materials enabling energy-efficient spintronic that go beyond conventional electronics.
Half metals are key to spintronics: Unlike traditional conductors, half metals allow only one spin orientation to pass through. This makes them ideal candidates for spintronics. However, all known half metals operate only at ultra-low temperatures and lose their special properties at the surface—limiting their use.
Now, for the first time, the team engineered a 2D half metal in the form of an ultrathin alloy of iron and palladium, just two atoms thick, on a palladium crystal. Using a state-of-the-art imaging technique called spin-resolved momentum microscopy, they showed that the alloy allows only one spin type to conduct, confirming the long-sought 2D half-metallicity.
"Remarkably, the material doesn't require a perfect crystal structure, which is a major advantage for real-world fabrication. Its special electronic properties can be fine-tuned by adjusting the iron content," explains Xin Liang Tan, Ph.D. student in the group of Dr. Christian Tusche at the Peter Grünberg Institute (PGI-6).
The discovery also overturns the long-standing assumption that spin–orbit coupling—an interaction between an electron's spin and its motion—hinders half-metallicity. "Instead, when carefully balanced with magnetic exchange from the iron atoms, spin–orbit coupling helps enable the effect, as we could show," adds Dr. Ying-Jiun Chen from the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-1) at Forschungszentrum Jülich.
The new material could serve as a foundation for spintronic components such as spin filters and spin-orbit torque systems, which are crucial for switching magnetic states in memory chips. Because it remains effective up to room temperature and integrates well with thin-film technologies, the alloy offers a promising route toward practical applications.
In addition, the material shows a rare feature: its spin polarization runs opposite to the direction of magnetization, a phenomenon that could unlock new functionalities in nanoscale magnetic devices.