Electron spin resonance in a model S=1/2 chain antiferromagnet with a uniform Dzyaloshinskii--Moriya interaction

TL;DR

This study investigates the electron spin resonance spectrum of a quasi-1D S=1/2 antiferromagnet, revealing an energy gap, a doublet of resonance lines, and interactions with spinon excitations influenced by a uniform Dzyaloshinskii--Moriya interaction.

Contribution

It provides experimental evidence linking ESR features to the two-spinon continuum in a model S=1/2 antiferromagnetic chain with Dzyaloshinskii--Moriya interaction.

Findings

Observation of an energy gap and doublet resonance lines in ESR spectrum.

Identification of the two-spinon continuum in the ESR data.

Detection of anisotropic paramagnetic defect resonance modes.

Abstract

The electron spin resonance spectrum of a quasi 1D S=1/2 antiferromagnet K2CuSO4Br2 was found to demonstrate an energy gap and a doublet of resonance lines in a wide temperature range between the Curie--Weiss and Ne\`{e}l temperatures. This type of magnetic resonance absorption corresponds well to the two-spinon continuum of excitations in S=1/2 antiferromagnetic spin chain with a uniform Dzyaloshinskii--Moriya interaction between the magnetic ions. A resonance mode of paramagnetic defects demonstrating strongly anisotropic behavior due to interaction with spinon excitations in the main matrix is also observed.