Structure and Magnetic Properties of Melilite-Type Compounds REBeGeO (RE = Pr, Nd, Gd-Yb) with Rare-Earth Ions on Shastry-Sutherland Lattice.

Rare-earth (RE)-based frustrated magnets, such as typical systems of combining strong spin-orbit coupling (SOC), geometric frustration, and anisotropic exchange interaction, can give rise to diverse exotic magnetic ground states such as quantum spin liquid. The discovery of new RE-based frustrated materials is crucial for exploring the exotic magnetic phases. Herein, we report the synthesis, structure, and magnetic properties of a family of melilite-type REBeGeO (RE = Pr, Nd, and Gd-Yb) compounds crystallized in a tetragonal 4̅2 structure, where magnetic RE ions lay out on the Shastry-Sutherland lattice (SSL) within the plane and are well separated by nonmagnetic [GeBeO] polyhedrons along the -axis. Temperature ()-dependent susceptibilities χ() and isothermal magnetization () measurements reveal that most REBeGeO compounds except RE = Tb show no magnetic ordering down to 2 K despite the dominant antiferromagnetic (AFM) interactions, where TbBeGeO undergoes AFM transition with Néel temperature ∼ 2.5 K and field-induced spin flop behaviors ( < ). In addition, the calculated magnetic entropy change Δ from the isothermal () curves reveals viable magnetocaloric effect for REBeGeO (RE = Gd and Dy) in liquid helium temperature regimes; GdBeGeO shows the maximum Δ up to 54.8 J K kg at Δ = 7 T and DyBeGeO has the largest value Δ = 16.1 J K kg at Δ = 2 T in this family. More excitingly, the rich diversity of RE ions in this family enables an archetype for exploring exotic quantum magnetic phenomena with large variability of spin located on the SSL lattice.