A Study of the Structure and Electronic and Thermal Properties of Quasi-One-Dimensional La3MoO7

The structure of La3MoO7was solved inP212121withZ=4 anda=7.597(1) Å,b=7.7192(4) Å andc=11.0953(8) Å and refined to the reliability factors ofR(F)=0.0366 andwR(F2)=0.0782 for 102 variables and 5352 reflections. A structural feature of interest is the presence of zigzag chains oftrans-corner-sharing octahedra of composition MoO5−5parallel to theb-axis. Resistivity data taken along theb-axis direction show semiconducting behavior in the range 140 to 298 K with an activation energy of 0.16 eV. The magnetic susceptibility is quite complex. The main feature is a broad maximum at 655 K which is interpreted as due to intrachain spin correlations of the Mo(5 +) ions. Assuming theS=1/2 Heisenberg model this implies aJ/k=−511 K. Several other anomalies are observed at 483, 140, and 100 K. Differential scanning calorimetry data also show the 483 K feature and disclose another at 373 K not seen in the susceptibility. There is no evidence from powder neutron diffraction data of any structural changes from 298 to 10 K but no data are available above room temperature. There is an indication from neutron diffraction data for the onset of long-range antiferromagnetic order below 100 K.