Abstract
When an ordered spin system of a given dimensionality undergoes a second order phase transition, the dependence of the order parameter, i.e., magnetization on temperature, can be well described by thermal excitations of elementary collective spin excitations (magnons). However, the behavior of magnons themselves, as a function of temperature and across the transition temperature , is an unknown issue. Utilizing spin-polarized high resolution electron energy loss spectroscopy, we monitor the high-energy (terahertz) magnons, excited in an ultrathin ferromagnet, as a function of temperature. We show that the magnons’ energy and lifetime decrease with temperature. The temperature-induced renormalization of the magnons’ energy and lifetime depends on the wave vector. We provide quantitative results on the temperature-induced damping and discuss the possible mechanism, e.g., multimagnon scattering. A careful investigation of physical quantities determining the magnons’ propagation indicates that terahertz magnons sustain their propagating character even at temperatures far above .
- Received 9 November 2016
DOI:https://doi.org/10.1103/PhysRevLett.118.127203
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Focus
Magnetic Fluctuations without a Magnet
Published 24 March 2017
Magnetic waves in a permanent magnet can survive even when the material is too hot for large-scale magnetism to exist.
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