Stacking disorder in novel ABAC-stacked brochantite, Cu4SO4(OH)6

In geometrically frustrated magnetic systems, weak interactions or slight changes to the structure can tip the delicate balance of exchange interactions, sending the system into a different ground state. Brochantite, Cu4 SO4 (OH)6, has a copper sublattice composed of distorted triangles, making it a likely host for frustrated magnetism, but it exhibits stacking disorder. The lack of synthetic single crystals has limited research on the magnetism in brochantite to powders and natural mineral crystals. We grew crystals which we find to be a new polytype with a tendency toward ABAC stacking and some anion disorder, alongside the expected stacking disorder. Comparison to previous results on natural mineral specimens suggests that cation disorder is more deleterious to the magnetism than anion and stacking disorder. Our specific heat data suggest a double transition on cooling into the magnetically ordered state. ©2025 American Physical Society.

Keywords

Copper, Crystals, Minerals, Synthesis, Magnetism, Anions, Crystal structure, Magnetism, Crystal growth, Specific heat, Scattering

Citation

Chakkingal, A. M., Fuller, C., Avdeev, M., Gumeniuk, R., Parui, K. K., Rahn, M. C., Pabst, F., Wang, Y., Granovsky, S., Korshunov, A., Chernyshov, D., Inosov, D. S., & Peets, D. C. (2025). Stacking disorder in novel ABAC-stacked brochantite, Cu4 SO4 (OH)6. Physical Review Materials, 9(5), 054407. doi:10.1103/PhysRevMaterials.9.054407