Structure-tuning magnetism in the Co(NbxTa1−x)2O6 series

Low dimensional quantum materials have been extensively studied within the physics community, among which $\mathrm{C}{\mathrm{o}}^{2+}$ is one of the most popular magnetic ions to be embedded into the structural motif. $\mathrm{CoN}{\mathrm{b}}_{2}{\mathrm{O}}_{6}$ and $\mathrm{CoT}{\mathrm{a}}_{2}{\mathrm{O}}_{6}$ both have adopted an effective spin-1/2 state, with the former attracting enduring interest while the latter being rarely investigated. This difference can be attributed to their distinct crystal structures, not only in crystal systems, but more important, how the $\mathrm{Co}{\mathrm{O}}_{6}$ octahedra are connected. We successfully merge these two compounds together and map out the doping limits. We find out Ta and Nb dopants modify the properties of the parent compounds in subtle but different ways and construct a magnetic phase diagram of the $\mathrm{Co}{(\mathrm{N}{\mathrm{b}}_{x}\mathrm{T}{\mathrm{a}}_{1\ensuremath{-}x})}_{2}{\mathrm{O}}_{6}$ $(0\ensuremath{\le}x\ensuremath{\le}1)$ series. In addition, our results suggest that Ta-doping may pave a way to strengthen the lower-dimensional quantum phenomena in $\mathrm{CoN}{\mathrm{b}}_{2}{\mathrm{O}}_{6}$ before its crystal structure starts to melt down.