Site-selective $d^{10}$/$d^0$ substitution in a $S=1/2$ spin ladder Ba${}_2$CuTe${}_{1-x}$W${}_x$O${}_6$ ($0\le x\le 0.3$)

Abstract

Remarkably, doping isovalent $d^{10}$ and $d^0$ cations onto the $B$'' site in $A_{2}B$'$B$''O${}_6$ double perovskites has the power to direct the magnetic interactions between magnetic $B$' cations. This is due to changes in orbital hybridization, which favors different superexchange pathways, and leads to the formation of alternative magnetic structures depending on whether $B$'' 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, a W${}^{6+}$ $d^0$ dopant was introduced to a $d^{10}$ 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). Neutron and synchrotron X-ray diffraction show that 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. This means the intra-ladder interactions are selectively tuned by the $d^0$ cations. Bulk magnetic measurements suggest this suppresses magnetic ordering in a similar manner to that observed for the spin-liquid like material Sr${}_2$CuTe${}_{1-x}$W${}_x$O${}_6$. This further demonstrates the utility of $d^{10}$ and $d^0$ dopants as a tool for tuning magnetic ground states in a wide range of perovskites and perovskite-derived structures.

26+24 pages, 7+20 figures