The series of compounds $A{\mathrm{Ag}}_2\mathrm{Cr}{\left[{\mathrm{VO}}_4\right]}_2$, with $A=\mathrm{Ag}$, K, or Rb, is layered S = 3/2 triangular-lattice (TL) systems in which the magnetic exchange interactions between ${\mathrm{Cr}}^{3+}\left(3d^3\right)$ ions are mediated by nonmagnetic ${\left[{\mathrm{VO}}_4\right]}^{3-}$ entities. Here, the relative orientation of the vanadate is altered with respect to the TL as a function of the $A$ site, which corresponds to an induced symmetry change of the $\left[{\mathrm{CrO}}_6\right]$ complex. All members of this series of compounds belong to the class of frustrated TL antiferromagnets. We find that the distorted TL ($A=\mathrm{Ag}$) exhibits collinear antiferromagnetic long-range order (LRO) at $T_N\approx 10$ K, whereas the high-symmetry cases ($A=\mathrm{K}$, Rb) evade LRO in zero field down to 0.03 K, the lowest temperature of our experiments. The latter members of the series belong to the undistorted TL and are candidates for spin-liquid ground states presumably not related to Ising anisotropy or dimerization.

• Received 12 February 2017
• Revised 22 May 2017

DOI:https://doi.org/10.1103/PhysRevB.96.064404