ANOMALOUS LOW-DIMENSIONAL SYSTEM - STUDY OF MAGNETISM AND ELECTRICAL-CONDUCTIVITY IN NA2RU4O9-DELTA

The magnetic susceptibility chi(parallel to)(H parallel to b), chi(per pendicular to)(H perpendicular to b) (2 less than or equal to T less t han or equal to 700 K) and electrical resistivity rho(T) (2 less than or equal to T less than or equal to 300 K) of single crystal Na2Ru4O9- delta (delta greater than or equal to 0) with various oxygen content w ere measured. The crystal structure of this compound is monoclinic wit h single, double, and triple chains along the b axis. The most strikin g feature of this compound is the drastically large anisotropy reflect ed in the resistivity which exhibits metallic behavior along chains an d semiconducting behavior perpendicular to the chains. The resistivity ratio for these two directions (rho(perpendicular to)/rho(parallel to )) is larger than 10(5). This ratio is exceptionally large, indicating that the anisotropy of the bandwidth is substantial. It is remarkable that, after reduction of oxygen content in the system, the magnetic s usceptibility undergoes a drastic change, whereas the electrical resis tivity along the conducting chains is altered only slightly. It is arg ued that the different sensitivity to oxygen content reflected in magn etic and transport properties may be attributed to the complexity of t he crystal structure. The striking observations presented here may sug gest a one-dimensional system that possesses unique physical propertie s. (C) 1996 American Institute of Physics.