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 RTa7O19 (R = Pr, Sm, Eu, Gd, Dy, Ho) compounds with space groupP6¯2c. 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, RTa7O19 provides a new platform for exploring the frustrated magnetism. •A new series of R-based triangular-lattice magnets, RTa7O19 (R = Pr, Sm, Eu, Gd, Dy, Ho) heptatantalate, were successfully synthesized and the magnetic R ions reside on the perfect 2D triangular layers separated by the nonmagnetic Ta polyhedra.•There are no signs of long-range magnetic ordering down to 2 K and field-induced magnetic transitions in all the compounds.•Due to disorder and significant AFM interaction (large θCW), there exists appropriate frustration in the compounds with R = Pr, Dy and Ho.