Abstract
Several previous studies reported that a one-dimensional Heisenberg chain model is inadequate in describing the magnetic properties of the low-dimensional quantum antiferromagnet $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$, but the origin for this observation has remained unclear. We have reinvestigated the magnetic properties of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ and found that our anisotropic magnetic susceptibility, neutron-powder diffraction, and electron paramagnetic spin-resonance measurements are in good agreement with extensive density-functional theory ($\mathrm{DFT}+U$) total energy calculations which indicate that the correct spin lattice model for $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ is rather a $S=1/2$ 2D-Heisenberg antiferromagnetic lattice. The magnetic susceptibility data are well described by a rectangular Heisenberg antiferromagnet with anisotropy ratio $\ensuremath{\alpha}\ensuremath{\sim}$ 0.7 consistent with the DFT results. Quantum Monte Carlo simulations of the magnetic susceptibilities for a rectangular lattice Heisenberg antiferromagnet were performed in the anisotropy range 0.5 $\ensuremath{\le}\ensuremath{\alpha}\ensuremath{\le}$ 1.0. The results of the Quantum Monte Carlo calculations were cast into a Pad\'e approximant which was used to fit the temperature-dependent magnetic susceptibility data. Neutron-powder-diffraction measurements were used to conclusively solve the collinear antiferromagnetic structure of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ below the N\'eel temperature of $\ensuremath{\sim}22.4$ K.
Highlights
Interest in low-dimensional quantum magnetic systems is motivated by the observation that such systems are model candidates to test theoretical predictions for exotic ground states with unusual excitations that are conceptually different from the standard behavior of three-dimensional (3D) magnetic systems [1,2,3,4]
Our magnetic structure solution for α-CuV2O6 based on a total of five magnetic Bragg reflections is essentially a C-type AFM structure characterized by a FM alignment of the Cu moments along the [100] (P-1 setting) direction, i.e., the direction of the closest Cu . . . Cu approach
Our magnetic structure solution agrees with Kikuchi et al.’s second magnetic structure proposal shown as Fig. 9(B) in Ref. [28]
Summary
Interest in low-dimensional quantum magnetic systems is motivated by the observation that such systems are model candidates to test theoretical predictions for exotic ground states with unusual excitations that are conceptually different from the standard behavior of three-dimensional (3D) magnetic systems [1,2,3,4]. One-dimensional (1D) arrangement of Cu2+ spin S = 1/2 ions in CuL2 ribbon chains (where L are ligands such as O, Cl, or Br) have recently proved to exhibit unusual magnetic and magnetoelectric ground-state properties [5,6,7,8,9,10,11,12,13,14,15]. Such ribbon chains are made up of square-planar CuL4 plaquettes sharing their opposite edges.
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