LAUSR

We investigate the structural and magnetic properties of the quantum magnet $\mathrm{Ba}\mathrm{Cu}{\mathrm{Te}}_{2}{\mathrm{O}}_{6}$. This compound is synthesized in powder and single crystal form for the first time. Synchrotron x-ray and neutron diffraction reveal a cubic crystal structure $(P{4}_{1}32)$ where the magnetic ${\mathrm{Cu}}^{2+}$ ions form a complex network. Heat capacity and static magnetic susceptibility measurements suggest the presence of antiferromagnetic interactions with a Curie-Weiss temperature of $\ensuremath{\approx}\ensuremath{-}33$ K, while long-range magnetic order occurs at the much lower temperature of $\ensuremath{\approx}6.3$ K. The magnetic structure, solved using neutron diffraction, reveals antiferromagnetic order along chains parallel to the $a,$ $b,$ and $c$ crystal axes. This is consistent with the magnetic excitations which resemble the multispinon continuum typical of the spin-1/2 Heisenberg antiferromagnetic chain. A consistent intrachain interaction value of $\ensuremath{\approx}34$ K is achieved from the various techniques. Finally the magnetic structure provides evidence that the chains are coupled together in a noncollinear arrangement by a much weaker antiferromagnetic, frustrated hyperkagome interaction.