Dimerization-enhanced exotic magnetization plateau and magnetoelectric phase diagrams in skew-chain Co2V2O7

The low-dimensional frustrated antiferromagnet system has been an appealing playground for investigating the exotic magnetic ground states. The $S=1/2$ skew chain Co₂V₂O₇ attracted considerable interest for its magnetization plateau and the emergent ferroelectricity under high magnetic fields. In this work, we report the comprehensive angular studies of the magnetization plateau and the ferroelectric polarization in Co₂V₂O₇ under high fields up to 30 T. The magnetization was studied in detail with the applied field rotated within the $bc$ and $ab$ planes. We find that the 1/2 magnetization plateau is enhanced with the field rotating within the $bc$ plane and becomes most pronounced when the field is titled 30^∘ away from the b axis (denoted as the b* axis). The temperature dependence of ferroelectric polarization was also studied along the $a, c$, and b* axes, respectively. Based on these polarization measurements, the magnetic field temperature phase diagrams have been constructed for the three axes. We propose a model which considers the decoupling of the two inequivalent Co spins to explain the exotic polarization flop and the phase diagrams. This decoupling is considered to be enhanced by the dimerization effect, and that the non-negligible interchain interaction J₃ plays a crucial role.