Effects of Ge doping in Yb₂Si₂Al, a mixed valence Shastry-Sutherland Lattice compound

Yb₂ Si₂Al s an intermediate valence Yb compound with Yb ions on the 2 dimensional Shastry-Sutherland lattice (SSL). The material does not order magnetically with temperatures as low as T= 2 K and shows signs of Kondo coherence and non-Fermi liquid behavior at low temperatures. Substituting Mg in Yb₂ Al_1-x Mg_xSi₂ drives the ground state to antiferromagnetic order. [1-3]

We synthesized several compositions of, Yb₂ Si_2-xGe_xAl and measured structural parameters, magnetic susceptibility χ, and specific heat C as functions of temperature. Single crystal x-ray diffraction shows correlation between doping, lattice constants, and atomic positions. Measurements of χ indicate a paramagnetic ground state is favored at large Ge concentrations, while C suggests correlation between Ge concentration and the splitting of the SSL singlet and triplet states. Taken together, our results indicate a connection between frustration in the SSL planes and Ge concentration.