Synthesis, structure and magnetic properties of the S=1/2, one-dimensional antiferromagnet, Y5Re2O12

Single crystals of Y5Re2O12 have been grown, and the crystal structure has been determined by X-ray diffraction. This compound crystallizes in space group C2/m with cell dimensions of a=12.4081(10) A b=5.6604(5) A, c=7.4951(6) A, β=107.837(3) deg., Z=2. The final refinement led to R1=0.0238, WR2=0.0459 for 1053 observed reflections with F>4σ(F 0). Edge-sharing ReO6 octahedra form infinite linear [ReO2O4/2] n chains along the b direction with alternating short and long Re-Re distances. Three crystallographically independent yttrium atoms surround O2 to form OY4 tetrahedra, which share edges and corners in the ab plane to form a two-dimensional Y5O4 network which separates the [ReO2O4/2] n magnetic chains. This compound is therefore isostructural with the series Ln5Re2O12 Ln=Gd-Lu, which have been known since 1969. The average Re oxidation state is +4.5 in the chains and a reasonable, if qualitative MO scheme results in one unpaired electron per Re dimer. Consistent with this, magnetic susceptibility data can be fitted to the one-dimensional antiferromagnetic Heisenberg model with S=1/2 and parameters Jintra/k=-89(1)K, g=2.15(4) and χ(TIP)=5(1)x10-4 emu/mol. There is no sign of long-range magnetic order down to 2 K. These results are contrasted with those for the isostructural Y5Mo2O12