Crystal structure, electric and magnetic properties, and Raman spectroscopy of Gd3RuO7

A member of the R3MO7 family containing two magnetic cations, Gd3RuO7, has been synthesized by high-temperature solid-state reaction. The structure has been determined by single-crystal methods: space group Cmcm(#63), a(0)=10.643(2) Angstrom, b(0)=7.345(1) Angstrom, c(0)=7.380(1) Angstrom, V=576.90(14) Angstrom (3), Z=4, R1 =0.021, wR2=0.047. The most important structural feature is the one-dimensional RuO6 chain running parallel to the c axis. Ln a wide temperature range the conductivity of Gd3RuO7 follows the dependence ln(rho)proportional toT(-1/2), which is typical for Mott variable-range hopping of localized carriers in one dimension. The magnetic susceptibility obeys the Curie-Weiss law with theta (p)= -7.5 K and Curie constant C-mol=25 emu K/mole. Magnetization data reveal two successive transitions at about 14.5 and 8 K, which indicates independent ordering of Ru and Gd moments, respectively. The analysis shows that in total 27 (8A(g) + 8B(1g) + 5B(2g) +6B(3g)) Raman-active modes are expected for Gd3RuO7. As a larger number of A(g) lines (10) are observed in the polarized Raman spectra, we suggest that two of the A(g) lines (at 233 and 780 cm(-1)) either arise from local vibrations or are of nonphonon origin.