Site-selective d¹⁰/d⁰ substitution in an S = ¹/₂ spin ladder Ba₂CuTe_1–xW_xO₆ (0 ≤ x ≤ 0.3)

Isovalent nonmagnetic d¹⁰ and d⁰ B″ cations have proven to be a powerful tool for tuning the magnetic interactions between magnetic B′ cations in A₂B′B″O₆ 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 d¹⁰ or d⁰. Furthermore, the competition generated by introducing mixtures of d¹⁰ and d⁰ cations can drive the material into the realms of exotic quantum magnetism. Here, Te⁶⁺ d¹⁰ was substituted by W⁶⁺ d⁰ in the hexagonal perovskite Ba₂CuTeO₆, which possesses a spin ladder geometry of Cu²⁺ cations, creating a Ba₂CuTe_1–xW_xO₆ solid solution (x = 0–0.3). We find W⁶⁺ is almost exclusively substituted for Te⁶⁺ 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 d⁰ orbitals modify the relative intraladder interaction strength (J_rung/J_leg) so the system changes from a spin ladder to isolated spin chains as W⁶⁺ increases. This further demonstrates the utility of d¹⁰ and d⁰ dopants as a tool for tuning magnetic interactions in a wide range of perovskites and perovskite-derived structures.