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The synthesis of aromatic monodispersed telechelic dithiols performed from the esterification of thioglycolic acid with aromatic monodispersed telechelic diols is presented. The diols were prepared from the transesterification of ethylene glycol with the dimethyl terephthalate. In all cases the yields are high and the products are carefully characterized by 1H and 13C-NMR.

Investigations made by susceptibility measurements and neutron diffraction experiments have been performed on the ternary germanide TbMn 6 Ge 6 of HfFe 6 Ge 6 -type structure ( P6/mmm ). TbMn 6 Ge 6 orders ferrimagnetically at T c ≈ 427 K but an antiferromagnetic state occurs below about 410 K. Neutron diffraction study shows that both rare earth and manganese sublattices order simultaneously at room temperature. Over the whole 2–300 K temperature range the magnetic structure is a flat spiral consisting of ferromagnetic (001) sheets (with the moments in the layers) of Mn and Tb atoms respectively stacked along the c axis in the sequence Mn1TbMn2Mn1TbMn2. At 2 K, according to the modulation vector k = (0, 0, ∼0.125), the magnetic moments change their orientation by about 45° within the basal plane on going from one Tb sheet to another, while one observes a spiral turn angle θ 1 ≈ 31° between adjacent Mn1TbMn2 layers and θ 2 ≈ 14° between Mn2Mn1 layers, i.e. a repeat distance of about 65 A. The moment values are μ Tb = 8.43(27) μ B and μ Mn = 1.84(18) μ B . The magnetic behaviour of TbMn 6 Ge 6 is similar to that observed for DyMn 6 Ge 6 above 100 K. In the latter case our refinements lead us to propose a new arrangement for the helimagnetic structure previously published, with a Dy magnetic moment corrected to about 9 μ B at 2 K. The results confirm the interplay between the magnetic coupling and the unit cell volume observed in GdMn 6 Ge 6 . A discussion and some comparisons with the parent RMn 6 Sn 6 compounds are given in conclusion.

Raman spectroscopy has been used to study the local structure in glassy compositions of the ternary system As 2 S 3 -Sb 2 S 3 -Tl 2 S. The evolution of the positions and shapes of the bands observed is attributed to modifications in the environment of arsenic and antimony corresponding to structural changes as the composition is varied.