YbCu4Au is a unique material exhibiting multiple quantum fluctuations simultaneously. In this study, we investigated the field-induced criticality in YbCu4Au, based on comprehensive micro and macro measurements, including powder X-ray diffraction (XRD), neutron powder diffraction (NPD), nuclear magnetic resonance, magnetization, resistivity, specific heat, muon spin rotation relaxation (muSR), and X-ray absorption spectroscopy (XAS). Single crystals of YbCu4Au were grown, and their crystal structure was determined using XRD, and NPD measurements. Magnetic successive transitions were observed below 1 T by specific heat, resistivity, NPD, and muSR measurements. XAS measurements further indicate that the valence of Yb ions (+2.93) remained unchanged above 2 T. Moreover, the change in quadrupole frequency observed in the previous study is attributable to the electric quadrupole, as the expected value of the electric quadrupole was finite under magnetic fields [S. Wada et al., Journal of Physics: Condensed Matter, 20, 175201 (2008).]. These experimental results suggest that YbCu4Au exhibited bicritical behavior near 1 T, arising from the competition between RKKY interaction, accounting for the magnetic phases, and the Zeeman effect.
@article{arxiv.2411.05280,
title = {Field-Induced Criticality in YbCu4Au},
author = {T. Taniguchi and K. Osato and H. Okabe and T. Kitazawa and M. Kawamata and S. Hashimoto and Y. Ikeda and Y. Nambu and D. P. Sari and I. Watanabe and J. G. Nakamura and A. Koda and J. Gouchi and Y. Uwatoko and S. Kittaka and T. Sakakibara and M. Mizumaki and N. Kawamura and T. Yamanaka and K. Hiraki and T. Sasaki and M. Fujita},
journal= {arXiv preprint arXiv:2411.05280},
year = {2024}
}