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PRINCIPAL PUBLICATION

Naturally occurring 2D semiconductor with antiferromagnetic ground state, B. Pacáková et al., npj 2D Mater. Appl. 9, 38 (2025); https:/doi.org/10.1038/s41699-025-00561-5

High-resolution synchrotron X-ray diffraction (XRD) and scattering at beamline BM01 were critical for identifying the solvent compositions that promote interlayer expansion and eventual delamination. The intense and highly collimated beam allowed resolution of subtle changes in the interlayer spacing, revealing the optimal solvent mixtures for swelling, and monitoring the structural integrity of the silicate layers during and after exfoliation. The measurements showed distinct swelling regimes – ranging from quasi-crystalline expansion to fully delaminated states – that could be tuned by both the solvent composition and the cation environment (Figure 48a,b). This structural discrimination is not achievable with laboratory sources.

Atomic force microscopy confirmed lateral uniformity and monolayer thicknesses of ~1.2 nm, consistent across multiple flakes. X-ray photoelectron spectroscopy verified the local chemistry and oxidation states. Optical absorption and photoluminescence spectroscopy showed that the exfoliated vermiculite is a wide-band-gap semiconductor (3.3–3.9 eV). Magnetic measurements, supported by Mössbauer spectroscopy, demonstrated an antiferromagnetic ground state that persists in the nanosheet state, marking a rare combination of magnetic order and wide band-gap behaviour in a natural 2D material. Density functional theory calculations linked these properties to the distribution and coordination of iron within the silicate layers, revealing how subtle distortions and cation substitutions tune the electronic band structure

and magnetic ordering. The modelling also showed that neither chemical doping nor multilayer engineering is required – both semiconducting and magnetic behaviour arise intrinsically from the mineral’s natural crystal chemistry.

This work identifies vermiculite as the first known naturally occurring 2D semiconductor with intrinsic antiferromagnetic order. Because the material is abundant, non-toxic, and produced using simple ion- exchange and swelling steps, it provides a sustainable platform for 2D electronics and spintronics. Its combination of wide band-gap, insulating behaviour, and magnetic ordering opens opportunities in ultraviolet optoelectronics, high-voltage and high- frequency electronics, and low-energy magnonic or spin-based information technologies.

More broadly, the study demonstrates that geological minerals represent an untapped and sustainable resource for advanced functional materials. The workflow established here – synchrotron-based structural analysis, nanosheet-level spectroscopy, and first-principles modelling – forms a reproducible strategy for evaluating other natural layered minerals for 2D semiconducting, magnetic, or multifunctional applications. This approach aligns with global efforts to identify low-resource, carbon-neutral materials and offers a fundamentally different route to 2D materials discovery, in which nature itself provides the structural and compositional template.

Fig. 48: a-b) Synchrotron XRD patterns collected at BM01 reveal how solvent composition controls the expansion of interlayer spacing during delamination.