Spin-wave lifetimes throughout the Brillouin zone.
We used a neutron spin-echo method with microelectron-volt 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 spin waves (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.
Bayrakci
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Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany. bayrakci@fkf.mpg.de
Keller
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Habicht
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Keimer
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