Field-Induced Criticality in YbCu4Au

TL;DR

This study investigates the field-induced criticality in YbCu4Au, revealing bicritical behavior near 1 T due to competing magnetic interactions, with comprehensive measurements confirming the stability of Yb valence and magnetic phase transitions.

Contribution

It provides the first detailed experimental analysis of field-induced quantum criticality in YbCu4Au, highlighting bicritical behavior and the interplay of RKKY and Zeeman effects.

Findings

Magnetic transitions occur below 1 T confirmed by multiple measurement techniques.

Yb valence remains stable above 2 T, indicating valence stability.

YbCu4Au exhibits bicritical behavior near 1 T due to competing interactions.

Abstract

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.