Magnetic behavior of volborthite Cu3V2O7(OH)2(H2O)2 determined by coupled trimers rather than frustrated chains

TL;DR

This study models the magnetic properties of volborthite using DFT calculations, revealing that its magnetization plateau arises from polarized trimers rather than frustrated chains, aligning well with experimental data.

Contribution

It introduces a microscopic model based on coupled trimers, challenging the previous frustrated chain perspective for volborthite's magnetic behavior.

Findings

Identification of four key magnetic exchanges (J, J2, J', J1)

Good agreement with experimental susceptibility and magnetization data

Magnetization plateau linked to polarized magnetic trimers

Abstract

Motivated by recent experiments on volborthite single crystals showing a wide 1/3-magnetization plateau, we perform microscopic modeling by means of density functional theory (DFT) with the single-crystal structural data as a starting point. Using DFT+U, we find four leading magnetic exchanges: antiferromagnetic J and J2, as well as ferromagnetic J' and J1. Simulations of the derived spin Hamiltonian show good agreement with the experimental low-field magnetic susceptibility and high-field magnetization data. The 1/3-plateau phase pertains to polarized magnetic trimers formed by strong J bonds. An effective J$\rightarrow\infty$ model shows a tendency towards condensation of magnon bound states preceding the plateau phase.