Synthesis, structure, and electronic properties of the Li 11 RbGd 4 Te 6 O 30 single crystal.

Materials with spin dimers have attracted much attention in the last several decades because they could provide a playground to embody simple quantum spin models. For example, the Bose-Einstein condensation of magnons has been observed in TlCuCl 3 with anti-ferromagnetic Cu 2 Cl 6 dimers. In this work, we have synthesized a new kind of single-crystal Li 11 RbGd 4 Te 6 O 30 with Gd 2 O 15 dimers. This material belongs to the rhombohedral system with the lattice parameters: a = b = c = 16.0948 Å and α = β = γ = 33.74°. First-principles calculations indicate that Li 11 RbGd 4 Te 6 O 30 is a wide-bandgap (about 4.5 eV) semiconductor. But unlike many other well studied quantum dimer magnets with an anti-ferromagnetic ground state, the Gd 2 O 14 dimers in Li 11 RbGd 4 Te 6 O 30 show ferromagnetic intra-dimer exchange interactions according to our calculations. Our work provides a new material which could possibly extend the studies of the spin dimers.