Microscopic spin interactions on a deformed Kagom\'{e} lattice of volborthite are investigated through magnetoelastic couplings. A negative longitudinal magnetostriction ΔL<0 in the b axis is observed, which depends on the magnetization M with a peculiar relation of ΔL/L∝M1.3. Based on the exchange striction model, it is argued that the negative magnetostriction originates from a pantograph-like lattice change of the Cu-O-Cu chain in the b axis, and that the peculiar dependence arises from the local spin correlation. This idea is supported by DFT+U calculations simulating the lattice change and a finite-size calculation of the spin correlation, indicating that the recently proposed coupled-trimer model is a plausible one.
@article{arxiv.1903.04934,
title = {Magnetoelastic couplings in the deformed Kagom\'{e} quantum spin lattice of volborthite},
author = {Akihiko Ikeda and Shunsuke Furukawa and Oleg Janson and Yasuhiro H. Matsuda and Shojiro Takeyama and Takeshi Yajima and Zenji Hiroi and Hajime Ishikawa},
journal= {arXiv preprint arXiv:1903.04934},
year = {2019}
}