Short-Range Antiferromagnetic Ordering of Netlike S = 1/2 Linear Trimeric Units in the Copper Germanate K2Cu3Ge4O12.

K2Cu3Ge4O12 was synthesized via a solid-state reaction in a high-temperature experiment at 1073 K. Crystal structure analysis provided the following data: space group Cmcm (no. 63), a = 1407.9(2), b = 578.0(1), c = 1389.2(1) pm, V = 1.1305 nm3, and Z = 4. The structure consists of alternating layers of netlike arranged trimeric [Cu3O8]10- units and layers of four-membered rings of GeO4 tetrahedra. The potassium cations connect the different structural moieties. Although both structural motifs are well-known, the way they are connected in K2Cu3Ge4O12 is unique. K2Cu3Ge4O12 was further characterized via vibrational spectroscopy and SEM-EDX measurements. Magnetic measurements exhibit an antiferromagnetic behavior at low temperatures along with an unusual pseudo-2D coupling.