Researchers at Forschungszentrum Jülich have successfully created the worlds's 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 findings, now published as 'Editors' Suggestion' in Physical Review Letters, 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, a next-generation information technology that leverages both the charge and the spin of electrons for data storage and processing. In conventional electronics, on the other hand, only the charge is used.
However, all known half metals operate only at ultra-low temperatures and loose their special properties at the surface—limiting their use. This was until now, when the team at Forschungszentrum Jülich 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.
Robust and tunable
"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, PhD 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.
Pathway to next-generation devices
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.
