Exploring the spin-1/2 frustrated square lattice model with high-field magnetization measurements

TL;DR

This study uses high-field magnetization measurements on layered vanadium phosphates to validate the frustrated square lattice model, revealing how frustration influences magnetization behavior and confirming theoretical predictions.

Contribution

The paper provides experimental validation of the frustrated square lattice model in layered vanadium phosphates and explores how frustration affects magnetization curves.

Findings

Saturation fields range from 4 to 24 T, matching low-field estimates.

High-field data align with the regular frustrated square lattice model.

Increased frustration leads to more pronounced bending of magnetization curves.

Abstract

We report on high-field magnetization measurements for a number of layered vanadium phosphates that were recently recognized as spin-1/2 frustrated square lattice compounds with ferromagnetic nearest-neighbor couplings (J_1) and antiferromagnetic next-nearest-neighbor couplings (J_2). The saturation fields of the materials lie in the range from 4 to 24 T and show excellent agreement with the previous estimates of the exchange couplings deduced from low-field thermodynamic measurements. The consistency of the high-field data with the regular frustrated square lattice model provides experimental evidence for a weak impact of spatial anisotropy on the nearest-neighbor couplings in layered vanadium phosphates. The variation of the J_2/J_1 ratio within the compound family facilitates the experimental access to the evolution of the magnetization curve upon the change of the frustration magnitude. Our results support the recent theoretical prediction by Thalmeier et al. [Phys. Rev. B, 77, 104441 (2008)] and give evidence for the enhanced bending of the magnetization curves due to the increasing frustration of the underlying spin system.