Site-Selective $d^{10}/d^0$ Substitution in an S = $\frac{1} {2}$ Spin Ladder Ba$_2$CuTe$_{1–x}$W$_x$O$_6$ (0 ≤ x ≤ 0.3)

Isovalent nonmagnetic d$^{10}$ and d$^0$ B″ cations have proven to be a powerful tool for tuning the magnetic interactions between magnetic B′ cations in A$_2$B′B″O$_6$ double perovskites. Tuning is facilitated by the changes in orbital hybridization that favor different superexchange pathways. This can produce alternative magnetic structures when B″ is d$^{10}$ or d$^0$. Furthermore, the competition generated by introducing mixtures of d$^{10}$ and d$^0$ cations can drive the material into the realms of exotic quantum magnetism. Here, Te$^{6+}$ d$^{10}$ was substituted by Wu$^{6+}$ d$^0$ in the hexagonal perovskite Ba$_2$CuTeO$_6$, which possesses a spin ladder geometry of Cu$^{2+}$ cations, creating a Ba$_2$CuTe$_{1–x}$W$_x$O$_6$ solid solution (x = 0–0.3). We find W$^{6+}$ is almost exclusively substituted for Te$^{6+}$ on the corner-sharing site within the spin ladder, in preference to the face-sharing site between ladders. The site-selective doping directly tunes the intraladder, J$_{rung}$ and J$_{leg}$, interactions. Modeling the magnetic susceptibility data shows the d$^0$ orbitals modify the relative intraladder interaction strength (J$_{rung}$/J$_{leg}$) so the system changes from a spin ladder to isolated spin chains as W$^{6+}$ increases. This further demonstrates the utility of d$^{10}$ and d$^0$ dopants as a tool for tuning magnetic interactions in a wide range of perovskites and perovskite-derived structures