Crystal structure and magnetism of the linear-chain copper oxides ${\mathrm{Sr}}_5{\mathrm{Pb}}_{3-x}{\mathrm{Bi}}_x{\mathrm{CuO}}_{12}$

The title quasi-one-dimensional copper oxides $(0\mathrm{}<~x<~0.4)$ were investigated by neutron diffraction and magnetic susceptibility studies. Polyhedral ${\mathrm{CuO}}_4$ units in the compounds were found to comprise linear chains at an interchain distance of approximately 10 Å. The parent-chain compound $\mathrm{}(x=0\mathrm{}),$ however, shows less-anisotropic magnetic behavior above 2 K, although it is of substantially antiferromagnetic $({\mu }_{\mathrm{eff}}=1.85\mathrm{}\hspace{0.5em}{\mu }_{\mathrm{B}}$ and ${\Theta }_{\mathrm{W}}=-46.4\hspace{0.5em}\mathrm{K})$ spin-chain system. A magnetic cusp gradually appears at about 100 K in T vs $\chi$ with the Bi substitution. The cusp $\mathrm{}(x=0.4\mathrm{})\mathrm{}$ is fairly characterized by and therefore suggests the spin-gap nature at $\Delta {/k}_{\mathrm{B}}\sim 80\hspace{0.5em}\mathrm{K}.$ The chain compounds hold electrically insulating in the composition range.