RE3Sb3Zn2O14 (RE = La, Pr, Nd, Sm, Eu, Gd): a new family of pyrochlore derivatives with rare earth ions on a 2D Kagome lattice

We report the synthesis and crystal structures of compounds of the type RE3Sb3Zn2O14 (La3Sb3Zn2O14, Pr3Sb3Zn2O14, Nd3Sb3Zn2O14, Sm3Sb3Zn2O14, Eu3Sb3Zn2O14, and Gd3Sb3Zn2O14), a series of novel rhombohedral pyrochlore derivatives with rare earth ions on a two-dimensional Kagome lattice. Synchrotron powder X-ray diffraction was used to solve the structures of the compounds. The rare earth ions are fully atomically ordered in a symmetric magnetic Kagome lattice. The nonmagnetic lattice contains one ion (Zn) that is displaced from the center of its coordination polyhedron in a random fashion. The structure differs from the common cubic A2B2O7 pyrochlore type because it forms a layered rather than three-dimensional structure through ordering of ZnRE3 in the A sites and ZnSb3 in the B sites. Magnetic property measurements indicate the compounds display dominantly antiferromagnetic interactions between spins, and no signs of magnetic ordering above 1.8 K except possibly the Pr and Eu cases. RE3Sb3Zn2O14 is the first series of this structure type in which the rare earth is the only magnetic ion in the structure. This family is therefore an archetype for exploring rare earth magnetism on a two-dimensional Kagome lattice.