Spin gap in a quasi-1D S=1/2 antiferromagnet K2CuSO4Cl2

TL;DR

This study investigates the magnetic excitation spectrum of a quasi-1D S=1/2 antiferromagnet, revealing a spin gap and anisotropic ESR shifts explained by a crossover between different magnetic resonance regimes.

Contribution

It provides the first experimental observation of a spin gap in K$_2$CuSO$_4$Cl$_2$ and explains the ESR features through a crossover between spinon-type and Larmor-type resonances.

Findings

Observation of a spin gap in ESR spectra.

Identification of anisotropic shifts in resonance magnetic field.

Explanation of features via crossover between magnetic resonance types.

Abstract

Electron spin resonance experiments in the quasi-1D S=1/2 antiferromagnet K$_2$CuSO$_4$Cl$_2$ reveal opening of a gap in absence of magnetic ordering, as well as an anisotropic shift of the resonance magnetic field. These features of magnetic excitation spectrum are explained by a crossover between a gapped spinon-type doublet ESR formed in a 1D antiferromagnet with uniform Dzyaloshinskii-Moriya interaction and a Larmor-type resonance of a quasi-1D Heisenberg system