High-field properties of spin-1/2 frustrated square lattice compounds

Quantum spin systems present a broad range of exotic phenomena upon the application of external magnetic field. High-field properties of numerous low-dimensional Heisenberg models are actively studied theoretically, but still poorly understood experimentally due to the lack of proper materials with feasible saturation fields. Recently, we proposed a bundle of vanadium compounds that show the physics of spin-1/2 frustrated square lattice model at the energy scale of 5–10 K. In this contribution, we present experimental results for high-field properties of these materials.
Magnetization curves of five frustrated square lattice compounds were recorded in either static or pulsed magnetic fields. Most of the compounds show the saturation at 15–25 T and present the ideal energy scale for high-field studies. The values of the saturation fields are in remarkable agreement with the previous estimates of individual exchange couplings, based on thermodynamic measurements in low fields. The consistency of the low-field and high-field results confirms the interpretation of the materials within the frustrated square lattice model, despite the actual crystal symmetry is low, and numerous non-equivalent exchange couplings are possible. The change of the frustration ratio within the same compound family enables to study the change of the magnetization curve as the frustration is enhanced. We show that the increase of the frustration ratio leads to the enhanced bending of the magnetization curve. This result agrees with the recent theoretical study of the model [1] and is further supported by the direct comparison of the experimental magnetization curves and simulations for finite-size clusters.