  We present the crystal structures and magnetic properties of RE3Sb3Mg2O14
(La3Sb3Mg2O14, Pr3Sb3Mg2O14, Sm3Sb3Mg2O14, Eu3Sb3Mg2O14, Tb3Sb3Mg2O14, and
Ho3Sb3Mg2O14), a family of novel materials based on a perfect geometry 2D rare
earth Kagome lattice. Structure refinements were performed by the Rietveld
method using X-ray diffraction data, indicating that the layered compounds are
fully structurally ordered. The compounds crystallize in a rhombohedral
supercell of the cubic pyrochlore structure, in the space group R-3m. As
indicated by magnetic susceptibility measurements, they exhibit predominantly
antiferromagnetic interactions between rare earth moments. Except for possibly
Pr3Sb3Mg2O14 and Eu3Sb3Mg2O14, none of the compounds show any signs of magnetic
ordering above 2 K. This RE3Sb3Mg2O14 family of compounds is similar to that of
RE3Sb3Zn2O14, except the series reported here features a fully ordered
distribution of cations in both the nonmagnetic antimony and magnesium sites
and the magnetic rare earth kagome sites. The compounds appear to be relatively
defect-free and are therefore model systems for investigating magnetic
frustration on an ideal 2D rare earth Kagome lattice.
