We studied A V13 O18 (A=Sr,Ba), in which V ions form a face-centered-cubic lattice with periodically missing ions. It was found that there is a phase transition in both SrV13 O18 (Tc =270 K) and BaV13 O18 (Tc =200 K), where anomalies are observed in resistivity and magnetic susceptibility. Resistivity shows a contrasting behavior in the low-temperature phase between SrV13 O18 (a metallic behavior) and BaV13 O18 (an insulating behavior). By synchrotron x-ray powder-diffraction measurement, it was found that V trimerization occurs at the phase transition of SrV13 O 18. On the other hand, BaV13 O18 does not show a large change in the x-ray powder diffraction but superlattice peaks at (0 1 2 1 2) was observed in the electron diffraction. Possible orbital states of the t2g electrons in the V ions are discussed.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2010 Sept 10|