New 2D Half-Metal Magnets Predicted to Keep Their Spin at 550 K

A team of theoretical materials scientists in China has proposed a family of atomically thin magnetic materials that could bring spintronics a decisive step closer to practical reality. Writing in the Journal of Materials Science, researchers from Lanzhou Jiaotong University and Shanghai Dianji University report first-principles evidence that four single-layer compounds—FeCoCl2, FeCoBr2, FeVSe2, and FeVTe2—are stable, fully spin-polarized half-metals whose magnetic ordering survives to remarkably high temperatures, reaching as high as 550 kelvin. That is well above room temperature, a threshold that has frustrated the two-dimensional magnetism community for more than a decade.

The significance of the result lies in how rare it is to satisfy all of the requirements at once. Two-dimensional magnetic materials are attractive because they can be thinned to a single atomic layer without losing their magnetism, opening the door to ultrathin memory cells, spin filters, and logic devices that conventional three-dimensional magnets cannot deliver. But most known two-dimensional ferromagnets lose their magnetic order far below room temperature, because thermal fluctuations easily overwhelm the weak magnetic coupling in such reduced dimensions. Chromium triiodide, the celebrated layered ferromagnet discovered in 2017, orders at only tens of kelvin in monolayer form. Even the more robust chromium ditelluride ultrathin films reported in 2021 hover near room temperature, leaving little margin for real devices that must run hot.

Half-metallicity adds a second, equally demanding condition. In a half-metal, one spin channel of electrons behaves like a metal with freely conducting states at the Fermi level, while the opposite spin channel behaves like a semiconductor with a forbidden gap. The result is a current made of electrons with a single spin orientation—one hundred percent spin polarization. For spintronics, this is the ideal source: conventional ferromagnets such as iron or cobalt produce spin-polarized currents, but only partially, so a large fraction of the charge carriers carry the wrong spin and dilute the signal. A half-metal, in principle, injects a perfectly filtered spin current, which is why the concept, first articulated by Pickett and Moodera in 2001, has been pursued so aggressively in Heusler alloys, oxides, and now two-dimensional materials.

The new study also demands a third property: large magnetic anisotropy energy, or MAE. Magnetic anisotropy is the energetic preference of a magnet’s moments to point along a particular crystallographic direction rather than rotating freely in the plane. In two dimensions this is not a nicety but a necessity. According to the Mermin-Wagner argument, a purely isotropic two-dimensional Heisenberg magnet cannot sustain long-range order at any finite temperature; anisotropy effectively opens a gap in the spectrum of spin waves and stabilizes the ordered state. Large MAE also underpins the perpendicular magnetic anisotropy exploited in modern magnetic tunnel junctions, the nanoscale elements at the heart of magnetoresistive random-access memory, where field-free switching of the magnetization is a key engineering goal.

To establish that the four candidate monolayers are physically plausible rather than mathematical artifacts, the authors performed a systematic stability triage using density functional theory. Formation energies confirmed thermodynamic stability—that the compounds sit at energetically sensible positions relative to competing phases. Phonon spectrum calculations, which examine the vibrational modes of the lattice, showed no imaginary frequencies, the signature that the structures are dynamically stable and will not spontaneously distort. Elastic constant calculations completed the picture by verifying mechanical stability, characterizing how the monolayers respond to in-plane stretching and shearing. Passing all three tests is the standard credential for a credible two-dimensional material prediction, and many proposed monolayers fail at one of these hurdles.

The electronic structure calculations then delivered the headline result: all four monolayers are half-metals with relatively wide half-metallic gaps. The width of this gap matters because it sets the robustness of the spin filtering. A narrow gap can be closed by thermal excitation, defects, doping, or interface effects, degrading the perfect polarization; a wide gap means the minority-spin channel remains firmly insulating even under realistic perturbations. The team also found substantial magnetic anisotropy energies in all four compounds, satisfying the stability requirement for finite-temperature two-dimensional order and aligning with the Bruno picture, in which anisotropy arises from spin-orbit coupling acting on the orbital moments of transition-metal atoms.

The predicted Curie temperatures are the figures that will draw the most attention. Using Monte Carlo simulations built on a Heisenberg model, with exchange interaction parameters extracted from first-principles calculations, the researchers estimated Curie temperatures of 550 K for FeCoCl2, 510 K for FeCoBr2, 550 K for FeVSe2, and 460 K for FeVTe2. Monte Carlo simulation is the standard tool for translating microscopic exchange couplings into macroscopic ordering temperatures, because it captures the fluctuations that simpler mean-field estimates overstate. Values in the 460 to 550 K range imply that the magnetic order should persist comfortably above room temperature, which sits at roughly 300 K, providing the thermal headroom that most two-dimensional ferromagnets lack.

Equally important for device designers is what happens when the materials are strained. Real two-dimensional crystals are never perfectly relaxed: they grow on substrates, are transferred between hosts, and are deliberately stretched or compressed to tune their properties. Strain engineering has become a versatile knob for adjusting band gaps, magnetism, and even inducing new phases in two-dimensional materials. The researchers therefore examined how tensile and compressive strain affect the electronic and magnetic properties of their four monolayers. Their calculations show that the half-metallicity and the high Curie temperatures remain generally robust under strain regulation, meaning the key functionalities do not hinge on fragile fine-tuning of the lattice. That robustness substantially improves the odds that the predictions survive contact with experimental synthesis.

The four compounds belong to recognizable chemical families. The FeVX2 monolayers (X = Se, Te) are transition-metal dichalcogenides, relatives of the widely studied VX2 systems in which magnetism was identified computationally more than a decade ago, while the FeCoZ2 monolayers (Z = Cl, Br) extend into the transition-metal trihalide territory where heavy halogens are known to boost magnetic anisotropy. Combining iron with cobalt or vanadium in a common lattice appears to strengthen the exchange interactions that set the ordering temperature, an approach conceptually similar to the strategy that gives Co-based Heusler compounds their high Curie temperatures in three dimensions. The work was supported by the National Natural Science Foundation of China, and the authors note that their data will be made available on request.

As with any computational prediction, the gap between a density functional theory result and a working device remains wide. Synthesizing these monolayers, characterizing their magnetism experimentally, and integrating them into heterostructures will be the decisive tests. But the study addresses the precise bottleneck that has stalled two-dimensional spintronics: the scarcity of materials combining high Curie temperature, large magnetic anisotropy, and perfect spin polarization in a single stable monolayer. If FeCoCl2, FeCoBr2, FeVSe2, or FeVTe2 can be grown in the laboratory with the properties predicted, they would join the short list of two-dimensional magnets viable for room-temperature operation, and spin-filter devices, ultrathin memory elements, and field-free switching architectures would gain a new generation of candidate materials built from earth-abundant transition metals and simple halogens and chalcogens.

Subject of Research: Computational prediction of two-dimensional magnetic half-metal monolayers with high Curie temperatures for spintronics

Article Title: Two-dimensional magnetic half-metals with high curie temperature: FeCoZ2 (Z=Cl, Br) and FeVX2 (X=Se, Te)

Article References: Yin, Q.-B., Huang, W.-C., Song, X.-L., & Wang, X.-F. (2026). Two-dimensional magnetic half-metals with high curie temperature: FeCoZ2 (Z=Cl, Br) and FeVX2 (X=Se, Te). Journal of Materials Science. https://doi.org/10.1007/s10853-026-13913-3

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13913-3

Keywords: two-dimensional materials, half-metals, spintronics, Curie temperature, magnetic anisotropy, first-principles calculations, density functional theory, Monte Carlo simulation, transition metal dichalcogenides, ferromagnetism, strain engineering, monolayers