Trial of hole-doping to 4-and 5-leg ladder compounds

The electrical resistivity and magnetic susceptibility measurements have been made for the spin-1/2 4- and 5-leg ladder compounds, La₈Cu₈C₂₀ and La₈Cu₇O₁₉, respectively. Hole-doping has been attempted by means of high oxygen pressure annealing and substitution of Li⁺¹ for Cu⁺²,La₈Cu_8-xLi_xO₂₀- For LaCu₈O₂₀ and La₈Cu₇O₁₉, the electrical resistivities exhibit semiconductive behaviors, and the magnetic susceptibilities have a broad peak at around 150K. For the annealed samples under high oxygen pressure, the electrical resistivity becomes more conductive than that for as-sintered samples. The Li-substituted samples La₈Cu_8-xLi_xO₂₀ with x=0.4, 0.8 and 1.2 also shows the semiconductive behavior, but it becomes more conductive with increasing the Li concentration x. The magnetic susceptibility shows the broad peak at around 150K for as-sintered sample, and spin-glass like behavior was observed at around 10K. This transition is shifted to low temperature with increasing Li concentration.