We use a neutron spin-echo method with μeV resolution to determine the lifetimes of spin waves in the prototypical antiferromagnet MnF2 over the entire Brillouin zone. A theory based on the interaction of magnons with longitudinal spin fluctuations provides an excellent, parameter-free description of the data, except at the lowest momenta and temperatures. This is surprising, given the prominence of alternative theories based on magnon-magnon interactions in the literature. The results and technique open up a new avenue for the investigation of fundamental concepts in magnetism. The technique also allows measurement of the lifetimes of other elementary excitations (such as lattice vibrations) throughout the Brillouin zone.
@article{arxiv.cond-mat/0606814,
title = {Spin-Wave Lifetimes Throughout the Brillouin Zone},
author = {S. P. Bayrakci and T. Keller and K. Habicht and B. Keimer},
journal= {arXiv preprint arXiv:cond-mat/0606814},
year = {2009}
}