Synthesis, structure and magnetism of RTa7O19 (R = Pr, Sm, Eu, Gd, Dy, Ho) with perfect triangular lattice

We present the synthesis, structure and magnetic properties of a hitherto unstudied family of rare-earth based RTa ₇O ₁₉ ( R = Pr, Sm, Eu, Gd, Dy, Ho) compounds with space group P 6 ¯ 2 c . The structural analysis reveals that magnetic R ions form layers of ideal two-dimensional triangular lattices in the ab-plane separated by several nonmagnetic polyhedra layers along the c -axis. The magnetic susceptibility and magnetization measurements indicate the absence of long-range magnetic order and field-induced magnetic transitions in all the studied compounds. The details about the magnetism strongly depend on the type of R ions. The presence of geometrical frustration is discussed. Thus, RTa ₇O ₁₉ provides a new platform for exploring the frustrated magnetism.