Researchers synthesize magnetic semiconducting lanthanide MXenes
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Researchers at Linköping University and collaborators have synthesized a new class of two-dimensional magnetic semiconductors — lanthanide MXenes (Ln2CT2) — using a bottom-up method from layered halides. The materials exhibit tunable optical band gaps of 1.26–1.71 eV and ferromagnetic hysteresis at 2 K, offering a platform for spintronic devices.
Synthesis Method
The team developed a bottom-up approach using layered lanthanide halides (LnCl3, LnBr3) as van der Waals building blocks, avoiding conventional HF etching that dissolves lanthanides. Multilayer Ln2CT2 (Ln = Gd, Tb, Dy, Ho, Er, Lu; T = Cl, Br) was produced with high crystallinity. This method overcomes the scarcity of MAX precursors and the susceptibility of lanthanides to acid etchants.
Electronic and Magnetic Properties
Optical absorption onsets range from 1.26 to 1.71 eV, with room-temperature resistivity between 0.329 and 36.1 Ω cm and a negative temperature coefficient. Low-temperature ferromagnetic hysteresis was observed at 2 K, with positive Curie–Weiss temperatures of 6–59 K. Theoretical calculations show that surface terminals open band gaps by exhausting d-electron states near the Fermi level, while localized 4f electrons drive spin splitting.
Spintronic Potential
The combination of semiconducting and ferromagnetic properties makes Ln2CT2 a candidate for spintronic devices, such as magnetic tunnel junctions and spin valves. The composition-tunable band gap and room-temperature resistivity allow tailoring for specific applications. This work expands the MXene family to include lanthanides with strong spin polarization.
What's Next
The team plans to explore device integration and scale-up synthesis. It remains unclear whether the materials retain magnetic order at higher temperatures or in monolayer form.
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Researchers synthesize magnetic semiconducting lanthanide MXenes
