New-Type Phase Transition of Li₂RuO₃ with Honeycomb Structure

Abstract

A new-type structural transition has been found in Li2RuO3 with honeycomb\nlattice of edge-sharing RuO6-octahedra. With decreasing temperature T, the\nelectrical resistivity exhibits an anomalous increase at T=Tc~540 K, suggesting\nthe (metal to insulator)-like transition and the magnetic susceptibility also\nshows a sharp decrease. Detailed structure analyses have revealed that the high\ntemperature space group C2/m changes to P21/m at Tc. The most striking fact is\nthat a significant reduction of the bond lengths is found between two of six\nRu-Ru pairs of the hexagon in the low temperature phase, indicating a new type\nphase transition by the mechanism of the formation of molecular orbits of these\nRu-Ru pairs.\n