Magnetic interactions in the $S = 1/2$ square-lattice antiferromagnets Ba$_2$CuTeO$_6$ and Ba$_2$CuWO$_6$: parent phases of a possible spin liquid

TL;DR

This study investigates the magnetic interactions in Ba$_2$CuTeO$_6$ and Ba$_2$CuWO$_6$, revealing their frustrated square-lattice antiferromagnetic nature and predicting a spin-liquid-like ground state in their solid solutions.

Contribution

It provides a combined theoretical and experimental analysis of the magnetic properties of these double perovskites, highlighting the role of orbital hybridisation in their magnetic frustration and potential for spin liquid behavior.

Findings

Ba$_2$CuTeO$_6$ and Ba$_2$CuWO$_6$ are frustrated square-lattice antiferromagnets.

Differences in orbital hybridisation drive opposing magnetic interactions.

Predicted spin-liquid-like ground state in Ba$_2$Cu(Te$_{1-x}$W$_x$)O$_6$ solid solutions.

Abstract

The isostructural double perovskites Ba$_2$CuTeO$_6$ and Ba$_2$CuWO$_6$ are shown by theory and experiment to be frustrated square-lattice antiferromagnets with opposing dominant magnetic interactions. This is driven by differences in orbital hybridisation of Te$^{6+}$ and W$^{6+}$. A spin-liquid-like ground state is predicted for Ba$_2$Cu(Te$_{1-x}$W$_x$)O$_6$ solid solution similar to recent observations in Sr$_2$Cu(Te$_{1-x}$W$_x$)O$_6$.