Magnetic-Field Dependence of Paramagnetic Properties Investigated by 63/65Cu-NMR on the Yb Zigzag-Chain Semiconductor YbCuS2

TL;DR

This study uses 63/65Cu-NMR to explore how magnetic fields influence the paramagnetic properties of YbCuS2, revealing anisotropic behavior, a field-dependent 50 K anomaly, and signs of complex quantum phenomena.

Contribution

First detailed NMR investigation of YbCuS2 under magnetic fields, uncovering anisotropic magnetic properties and field-induced quantum effects in this zigzag-chain semiconductor.

Findings

Knight shift proportional to bulk susceptibility

Suppression of 50 K anomaly by magnetic fields

Enhanced 1/T1 at low temperatures above 3 T

Abstract

To investigate the paramagnetic properties of YbCuS2 under magnetic fields, we have performed the 63/65Cu-nuclear magnetic resonance (NMR) measurements. The NMR spectra can be reproduced by the simulations of the three-dimensional powder pattern and the additional two-dimensional powder pattern, indicating the partial sample orientation due to the anisotropy of the magnetic properties. These simulations suggest that the ac plane is the easy plane in YbCuS2. The Knight shift K is proportional to the bulk magnetic susceptibility and field-independent. The broad maximum of the nuclear spin-lattice relaxation rate 1/T1 at Tmax ~ 50 K (50 K anomaly) observed at zero magnetic field is quickly suppressed by the magnetic fields. This indicates that the 50 K anomaly is field-dependent. Furthermore, an anomalous enhancement of 1/T1 at low temperatures was observed above 3 T. This field seemingly corresponds to the magnetic field at which a field-induced phase transition occurs below the antiferromagnetic transition temperature TN ~ 1 K. The changes in 1/T1 observed in the paramagnetic state suggest the presence of the complex quantum phenomena under magnetic fields in YbCuS2.