La<sub>4</sub>Cu<sub>3-</sub><i><sub>x</sub></i>Zn<i><sub>x</sub></i>MoO<sub>12</sub>: Zinc-Doped Cuprates with Kagomé Lattices
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Two solid solutions, La4Cu3-xZnxMoO12 (0.05 ≤ x ≤ 0.20, SS1) and La4Cu3-xZnxMoO12 (0.30 ≤ x ≤ 2.40, SS2), were synthesized at ambient pressure and at temperatures from 1025 to 1200 °C by traditional solid-state reactions. Their structures were determined from X-ray powder diffraction with the help of electron and neutron diffraction. The atomic arrangements of SS1 and SS2 are similar, but their space groups are different, Pmnm for SS1 and P-1 for SS2, respectively. The copper, zinc, and molybdenum are coordinated by oxygen in corner-sharing trigonal bipyramids that are sandwiched between layers of lanthanum cations. In the transition metal cations layer of SS2, the copper and zinc cations order into a Kagomé-like lattice of triangular clusters. The magnetism has been measured from 2 to 300 K and is highly influenced by the geometric arrangement of the CuII and ZnII cations. The number of free electrons per three Cu atoms is close to one for all samples in SS1 and SS2 indicating that the system can be well expressed by independent CuII3 clusters. Spontaneous magnetization was observed in the system.
