We present a new model compound with the S = 1/2 frustrated square lattice composed of the charge-transfer salt (o-MePy-V)PF6. Ab initio calculations indicate the formation of an S = 1/2 square lattice, in which six types of nearest-neighbor ferromagnetic- and antiferromagnetic interactions cause frustration. By applying a magnetic field, we observe an unusually gradual increase of magnetization and a subsequent 1/2-plateau-like behavior. A numerical analysis using the tensor network method qualitatively demonstrates such behaviors and suggests a collinear ordered state and a field-enhanced quantum fluctuation. Furthermore, the local magnetization and T1^-1 probed by nuclear magnetic resonance measurements support these findings.
@article{arxiv.1808.06812,
title = {Field-enhanced quantum fuctuation in S=1/2 frustrated square lattice},
author = {H. Yamaguchi and Y. Sasaki and T. Okubo and M. Yoshida and T. Kida and M. Hagiwara and Y. Kono and S. Kittaka and T. Sakakibara and M. Takigawa and Y. Iwasaki and Y. Hosokoshi},
journal= {arXiv preprint arXiv:1808.06812},
year = {2018}
}