Magnetic anisotropy and quantized spin waves in hematite nanoparticles

Stine Nyborg Klausen, Kim Lefmann, Per-Anker Lindgård, Luise Theil Kuhn, Christian Robert Haffenden Bahl, Cathrine Frandsen, Steen Mørup, B. Roessli, N. Cavadini, C. Niedermayer

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We report on the observation of high-frequency collective magnetic excitations, (h) over bar omegaapproximate to1.1 meV, in hematite (alpha-Fe2O3) nanoparticles. The neutron scattering experiments include measurements at temperatures in the range 6-300 K and applied fields up to 7.5 T as well as polarization analysis. We give an explanation for the field- and temperature dependence of the excitations, which are found to have strongly elliptical out-of-plane precession. The frequency of the excitations gives information on the magnetic anisotropy constants in the system. We have in this way determined the temperature dependence of the magnetic anisotropy, which is strongly related to the suppression of the Morin transition in nanoparticles of hematite. Further, the localization of the signal in both energy and momentum transfer brings evidence for finite-size quantization of spin waves in the system.
Original languageEnglish
JournalPhysical Review B Condensed Matter
Issue number21
Pages (from-to)214411
Number of pages6
Publication statusPublished - 2004

Bibliographical note

Copyright (2004) American Physical Society.




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