Lu/Se Substitution Effect on Magnetic Properties of Yb-Based Zigzag Chain Semiconductor YbCuS2

TL;DR

This study explores how Lu and Se substitutions affect the magnetic properties of YbCuS2, revealing changes in antiferromagnetic transition temperature and quasiparticle excitations, with implications for understanding magnetic states in this material.

Contribution

It provides the first microscopic investigation of Lu/Se substitution effects on YbCuS2's magnetic properties, highlighting their impact on lattice expansion and magnetic excitations.

Findings

Se substitution causes larger lattice expansion than Lu.

Antiferromagnetic transition temperature decreases with substitution.

Gapless quasiparticle excitations persist despite substitutions.

Abstract

We have investigated the changes in the magnetic properties on YbCuS2 by Lu or Se substitutions from a microscopic perspective. In general, it is expected that nonmagnetic Lu substitution dilutes the magnetic Yb3+ concentration, and that Se substitution induces the negative pressure in YbCuS2. The 63/65Cu-nuclear quadrupole resonance (NQR) measurements on polycrystalline Yb0.9Lu0.1CuS2 and YbCu(S0.9Se0.1)2 revealed that the Se substitution leads to larger lattice expansion compared to the Lu substitution. The antiferromagnetic transition temperature TN decreased from 0.95 K in the unsubstituted system to 0.75 K in both substituted systems. Furthermore, the T-linear behavior of the 63Cu-NQR spin-lattice relaxation rate 1/T1, suggesting the presence of the gapless quasiparticle excitations, was observed even in the substituted systems, and the value of 1/T1T increases. These results under the chemical substitutions are opposite to those under pressure as previously reported, and are consistent with the expectation. Our systematic study indicates a clear relationship between the magnetic ordered states and the quasiparticle excitations in YbCuS2.