Syntheses and properties of a family of new compounds RE 3 Sb 3 Co 2 O 14 ( RE =La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure

Isostructural compounds RE3Sb3Co2O14 (RE=La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure were synthesized. The structure of La3Sb3Co2O14 was solved ab initio based on powder XRD data, and refined by combining with high resolution neutron diffraction data. La3Sb3Co2O14 crystallizes in the space group R-3m with the unit cell parameters a=7.52954(2)Å and c=17.59983(6)Å. The structures of other members in this family are confirmed by Rietveld refinement using powder X-ray diffraction data. The cations (RE, Sb and Co) in RE3Sb3Co2O14 are orderly distributed, presenting as [RE3Co][Sb3Co]O14 formula, and giving rise to two distinctive Kagome lattices constructed by RE3+ and Sb5+, respectively. Co2+ occupies 8-coordinated and 6-coordinated environments, showing low spin (S=1/2) and high spin (S=3/2) states respectively. The magnetic susceptibility and UV–visual spectroscopy supports the magnetic observation. TDDFT calculation was performed to interpret the electronic states. The compounds [RE3Co][Sb3Co]O14 provide a profound example in which the ideal 2D Kagome lattice is derived from the 3D pyrochlore-type structure by an ordered distribution of the metal cations.