Spin-Waves in the Mid-Infrared Spectrum of Antiferromagnetic YBa$_2$Cu$_3$O$_{6.0}$

TL;DR

This study measures the mid-infrared spin-wave spectrum of antiferromagnetic YBa₂Cu₃O₆.0, identifying magnon energies and confirming theoretical models, thereby providing insights into magnetic interactions in this material.

Contribution

The paper presents the first detailed mid-infrared spin-wave spectrum of YBa₂Cu₃O₆.0, including experimental magnon energies and comparison with linear spin wave theory to determine exchange interactions.

Findings

Single magnon excitation at 178 meV

Two-magnon peaks at 346 and 470 meV

Exchange constant J approximately 120 meV

Abstract

The mid-infrared spin-wave spectrum of antiferromagnetic YBa$_2$Cu$_3$O$_{6.0}$\ was determined by infrared transmission and reflection measurements ($\bbox{k} \!\! \parallel $c) at $T\!=\!10\!$~K.\@ Excitation of single magnons of the optical branch was observed at $E_{\text{op}}\!=\!178.0\!$~meV.\@ Two further peaks at $346\!$~meV ($\approx\!1.94\,E_{\text{op}}$) and $470\!$~meV ($\approx\!2.6\,E_{\text{op}}$) both belong to the two-magnon spectrum. Linear spin wave theory is in good agreement with the measured two-magnon spectrum, and allows to determine the exchange constant $J$ to be about $120\!$~meV, whereas the intrabilayer coupling $J_{12}$ is approximately $0.55\,J$.