G. Wltschek

The crystal structure of Tm5Re2O12.

The crystal structure of Tm(5)Re(2)O(12), pentathulium dirhenium dodecaoxide, was determined by synchrotron diffraction on a reticular merohedral twin, revealing space group C2/m with a = 12.3717 (7), b = 5.6744 (3), c = 7.4805 (4) Å, beta = 107.816 (2) degrees and Z = 2. Distorted ReO(6) octahedra form chains with alternating rhenium-rhenium distances of 2.455 (1) and 3.219 (1) Å. Early reports on Ln(2)ReO(5) compounds are critically reviewed in the light of our results for Tm(5)Re(2)O(12).

The crystal and magnetic structure relationship in Cu(W1-xMox)O4 compounds with wolframite-type structure

The magnetic structures of Cu(W1-xMox)O4 compounds with wolframite-type structure at 1.5 K have been determined by neutron powder diffraction for average composition x = 0.15, 0.25 and 0.35. For x = 0.15 the magnetic structure is antiferromagnetic with a magnetic unit cell doubled along the a-axis, = (1/2, 0, 0), i.e. the same magnetic structure as for CuWO4. For x = 0.25 and 0.35 two magnetic structures are observed: one is identical to that for x = 0.15, while the other is doubled with respect to the c-axis, = (0, 0, 1/2), i.e. the same magnetic structure as for the high-pressure modification CuMoO4 III. The coexistence of these two magnetic arrangements is interpreted as reflecting a slightly inhomogeneous contribution of Mo and W in different crystallites together with a sharp transition between the stability ranges of the two types of magnetic structure with respect to x. The specific Mo:W distributions in the grains of the powdered samples were deduced from a profile analysis based on high-resolution synchrotron powder diffraction data. No additional, intermediate magnetic phase with = (1/2, 1/2, 0) was found in Cu(W0.75Mo0.25)O4, in contrast to predictions in the framework of extended Huckel calculations based on the precise crystal structure.