Two-magnon excitations observed by neutron scattering in the two-dimensional spin-5/2 Heisenberg antiferromagnet Rb2MnF4

TL;DR

This study uses neutron scattering to observe both one-magnon and two-magnon excitations in the 2D spin-5/2 Heisenberg antiferromagnet Rb2MnF4, confirming theoretical predictions.

Contribution

First experimental observation of two-magnon continuum in a 2D spin-5/2 antiferromagnet using neutron scattering.

Findings

Detection of sharp one-magnon peaks

Observation of a weak two-magnon continuum

Results align with spin wave theory predictions

Abstract

The low-temperature magnetic excitations of the two-dimensional spin-5/2 square-lattice Heisenberg antiferromagnet Rb2MnF4 have been probed using pulsed inelastic neutron scattering. In addition to dominant sharp peaks identified with one-magnon excitations, a relatively weak continuum scattering is also observed at higher energies. This is attributed to neutron scattering by pairs of magnons and the observed intensities are consistent with predictions of spin wave theory.