Magnetic resonance and structural study of the cluster fluoride Nb6F15

In this work, we report updated structural data, obtained by single-crystal X-ray diffraction, on the binary fluoride Nb6F15 as well as measurements of 19F NMR over the temperature range 100–300 K, and EMR measurements over the temperature range 4–300 K. Nb6F15 is built up from Nb6F12iF6a octahedral cluster units sharing all apical fluorine ligands to form linear Nb–Fa–Nb interunit bridges (Fi: inner fluorine located in edge-bridging position, Fa: apical fluorine located in terminal position). The 19F NMR results showed two resonance lines. One line corresponds to the inner fluorine Fi in the (Nb6F12)−3 cluster core. The second 19F NMR line corresponds to the apical Fa. The shift of the NMR signal from Fi depends on the temperature and exhibits a Curie type behavior, while the position of the NMR signal from Fa is temperature independent. EMR measurements show a single Lorentzian line. The temperature dependence of the inverse of the intensity of the EMR line shows a Curie–Weiss behavior and an onset to an antiferromagnetic (AF) order at 5 K.