Issue |
Europhys. Lett.
Volume 60, Number 3, November I 2002
|
|
---|---|---|
Page(s) | 446 - 452 | |
Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
DOI | https://doi.org/10.1209/epl/i2002-00284-x | |
Published online | 01 October 2002 |
Longitudinal spin fluctuations in the antiferromagnet
studied by polarized neutron scattering
1
Institut für Festkörperforschung des Forschungszentrums
Jülich 52425 Jülich, Germany
2
Petersburg Nuclear Physics Institute - Gatchina,
St. Petersburg 188300, Russia
3
CEA-Grenoble, DRFMC-SPSMS-MDN - 38054 Grenoble Cedex 9, France
Received:
28
May
2002
Accepted:
13
August
2002
In neutron scattering experiments using polarization analysis we
separated the spectra of transverse and longitudinal magnetic
fluctuations in the anisotropic antiferromagnet .
While transverse modes are related to single-magnon scattering,
the longitudinal part is essentially due to two-magnon scattering.
They were measured at T= 30
and 50
well below the
Néel temperature
. The dynamic magnetic
response due to two-magnon creation or annihilation is separated
by a gap centered near the spin-wave frequency from the central
peak corresponding to neutron-magnon scattering (creation of one
magnon and annihilation of another). The longitudinal energy
spectrum extends to about twice the frequency of the zone
boundary modes. This tail at high energies is fairly independent
of momentum transfer. The observed longitudinal spectra are in
qualitative agreement with the theory for two-magnon processes
and are determined for large energy transfers ω by the
density of states
.
PACS: 75.30.Ds – Spin waves / 75.50.Ee – Antiferromagnetics / 75.40.Gb – Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
© EDP Sciences, 2002
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