| In recent years, considerable efforts were spent to search for materials with a kagome arrangement of spin-1/2 ions. Such systems are expected to imply exotic magnetic properties arising from the magnetic frustration and the magnetic ground state where constituent spins do not freeze (the spin liquid). The suggested real material realizations of a spin-1/2 kagome lattice are scarce. Among the most prominent materials are the natural mineral herbertsmithite, its polymorph kapellasite, haydeeite and volborthite. Using density functional theory calculations, we study the magnetism of these systems on a microscopic level. This way, we find that peculiarities of the crystal structure have a drastic impact on the magnetic coupling regime, and often give rise to unexpected ferromagnetic or long-range couplings. The resulting microscopic spin models can be used as a solid basis for a correct interpretation of relevant experiments. |
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