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) Angstrom b = 5.6604(5) Angstrom, c = 7.4951(6) Angstrom, beta =107.837(3)degrees, Z = 2. The final refinement led to R1 = 0.0238, WR2 = 0.0459 for 1053 observed reflections with F > 4sigma(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 Ln(5)Re(2)O(12) 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 J(intra)/k = -89(1)K, g = 2.15(4) and chi(TIP)=5(1) x 10(-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. (C) 2003 Elsevier Science (USA). All rights reserved.