Synthesis, crystal structure, and magnetic properties of novel 2D kagome materials RE sub(3)Sb sub(3)Mg sub(2)O sub(14) (RE=La, Pr, Sm, Eu, Tb, Ho): Comparison to RE sub(3)Sb sub(3)Zn sub(2)O sub(14) family

The crystal structures and magnetic properties of RE sub(3)Sb sub(3)Mg sub(2)O sub(14) (RE=La, Pr, Sm, Eu, Tb, Ho) with a perfect kagome lattice are presented and compared to RE sub(3)Sb sub(3)Zn sub(2)O sub(14). Rietveld structure refinements were performed 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. Magnetic susceptibility measurements show no signs of magnetic ordering above 2K. The RE sub(3)Sb sub(3)Mg sub(2)O sub(14) family is similar to that of RE sub(3)Sb sub(3)Zn sub(2)O sub(14); however, the series reported here features a fully ordered distribution of cations in both the nonmagnetic antimony and magnetic rare earth kagome lattices. Unlike the offsite disorder that Zn super(2+) experiences in RE sub(3)Sb sub(3)Zn sub(2)O sub(14), the magnesium sites in RE sub(3)Sb sub(3)Mg sub(2)O sub(14) are completely ordered. Here we compare the magnetic properties in both series of kagome compounds to determine how significant Zn super(2+)'s positional ordering is within this structure type. The compounds reported here appear to be relatively defect-free and are therefore model systems for investigating magnetic frustration on an ideal 2D rare earth kagome lattice.