Low-Temperature Magnetic Characterization of the Rare-Earth Melitite-Like RE₂Be₂GeO₇(RE = Dy, Gd, Ho, Yb, and Er)

A 2-D Heisenberg Hamiltonian with nearest-neighbour(J) and next-nearest-neighbour(J') interactions has an exactly solvable groundstate, which corresponds to a Heisenberg antiferromagnet when J'>>J, and a dimer singlet state when J>>J'. This theoretical model is attributed to Shastry and Sutherland and is referred to as the Shastry-Sutherland lattice (SSL). Materials which exhibit the SSL are of interest due to their potential to host spin-liquid states- and their associated spin-gaps- in the singlet state, as exemplified by SrCu2(BO3)2. The rare-earth Melitites, RE2Be2GeO7, are recently proposed spin-liquid candidates, hence they exhibit the Shastry-Sutherland lattice motif. However, true low-temperature data is not currently embodied by the available literature. Here, we present macroscopic and microscopic magnetic characterisation of some members (Dy, Gd, Ho, Yb, and Er) of the rare-earth melitite family, down to hundreds-to-tens of millikelvin scale.