Lifetimes of antiferromagnetic magnons in two and three dimensions: experiment, theory, and numerics

TL;DR

This study combines experiment, theory, and numerics to measure and understand magnon lifetimes in 2D and 3D antiferromagnets across the full Brillouin zone and temperature range.

Contribution

It rederives and extends theories of magnon lifetime due to magnon-magnon scattering, achieving quantitative agreement with experimental data.

Findings

Magnon lifetimes vary across the Brillouin zone and temperature.

Theoretical models accurately predict experimental results.

Collisions with domain boundaries have a minor impact.

Abstract

A high-resolution neutron spectroscopic technique is used to measure momentum-resolved magnon lifetimes in the prototypical two- and three-dimensional antiferromagnets Rb2MnF4 and MnF2, over the full Brillouin zone and a wide range of temperatures. We rederived theories of the lifetime resulting from magnon-magnon scattering, thereby broadening their applicability beyond asymptotically small regions of wavevector and temperature. Corresponding computations, combined with a small contribution reflecting collisions with domain boundaries, yield excellent quantitative agreement with the data.