Effect of hole doping inLixCu1−xO

A comprehensive study of the effect of hole doping on cupric oxide CuO, which may be an important reference compound for copper oxide superconductors, is done by experiments on the structural, transport conduction, and magnetic susceptibility properties of ${\mathrm{Cu}}_{1-x}{\mathrm{Li}}_x\mathrm{O}.$ With a conventional solid-state reaction process for sample preparation, lithium is found to substitute copper up to $x=1.7\%.\mathrm{}$ This small quantity of substitution substantially brings out changes in crystal structure, transport conduction, and magnetic transition. With 1.7% Li substitution, the resistivity and activation energy decrease in orders of magnitude, the antiferromagnetic transition temperatures decrease from $T_{N1\mathrm{}}=229\mathrm{}\mathrm{K},$ $T_{N2\mathrm{}}=213\mathrm{}\mathrm{K}$ to $T_{N1\mathrm{}}=206\mathrm{}\mathrm{K},$ $T_{N2\mathrm{}}=199\mathrm{}\mathrm{K},$ respectively, and the lattice constants show contrasting anisotropic changes. While the substitution of Cu by Li decreases the unit cell volume, it remarkably increases the Cu-Cu distance along the superexchange direction [101¯]. The relatively large decrement in $T_N$ is consistently explained by the weakened quasi-one-dimensional superexchange coupling along [101¯].