Synthesis, crystal structure, and magnetic properties of novel 2D kagome materials RE3Sb3Mg2O14 (RE = La, Pr, Sm, Eu, Tb, Ho): Comparison to RE3Sb3Zn2O14 family.

The crystal structures and magnetic properties of RE3Sb3Mg2O14 (RE = La, Pr, Sm, Eu, Tb, Ho) with a perfect kagome lattice are presented and compared to RE3Sb3Zn2O14. 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-3 m. Magnetic susceptibility measurements show no signs of magnetic ordering above 2 K. The RE3Sb3Mg2O14 family is similar to that of RE3Sb3Zn2O14; 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 Zn2+ experiences in RE3Sb3Zn2O14, the magnesium sites in RE3Sb3Mg2O14 are completely ordered. Here we compare the magnetic properties in both series of kagome compounds to determine how significant Zn2+'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. [ABSTRACT FROM AUTHOR]