Ground states of the Shastry-Sutherland lattice materials Gd2Be2GeO7 and Dy2Be2GeO7

The recent realization that the rare-earth melilites RE2Be2GeO7 host the Shastry-Sutherland lattice within planes of RE3+ ions has sparked a number of studies. This family of materials lacks appreciable site mixing and conductivity, making them promising candidates for the Shastry-Sutherland model. Herein, we present the magnetic ground states of two of these rare-earth melilites: RE = Gd and Dy. We find, through measurements of magnetic susceptibility, magnetization, and specific heat capacity (RE = Dy only), that these two melilites are antiferromagnets (TN ≈1 K). Gd2Be2GeO7, in accordance with its electronic configuration, has isotropic single-ion anisotropy but shows a quadratic contribution to its magnetization. Dy2Be2GeO7 has Ising-like single-ion anisotropy and is likely an effective spin-1/2 system. Both materials exhibit metamagnetic transitions. We identify this transition in Dy2Be2GeO7, occurring at 86(1) mT for T=500 mK, to likely be a spin-flip transition.