This title appears in the Scientific Report :
2015
Please use the identifier:
http://hdl.handle.net/2128/8613 in citations.
Please use the identifier: http://dx.doi.org/10.1103/PhysRevB.91.094421 in citations.
Dynamic rotor mode in antiferromagnetic nanopartciles
Dynamic rotor mode in antiferromagnetic nanopartciles
We present experimental, numerical, and theoretical evidence for an unusual mode of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering experiments on 8-nm particles of hematite display a loss of diffraction intensity with temperature, the intensity vanishing around 150 K. Howeve...
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Personal Name(s): | Lefmann, K. (Corresponding Author) |
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Jacobsen, H. / Garde, J. / Hedegard, P. / Wischnewski, Andreas / Ancona, S. N. / Jacobsen, H. S. / Bahl, C. R. H. / Theil Kuhn, L. | |
Contributing Institute: |
Neutronenstreuung; ICS-1 Neutronenstreuung; JCNS-1 |
Published in: | Physical Review B Physical review / B, 91 91 (2015 2015) 9 9, S. 094421 094421 |
Imprint: |
College Park, Md.
APS
2015
|
DOI: |
10.1103/PhysRevB.91.094421 |
Document Type: |
Journal Article |
Research Program: |
Soft Matter, Health and Life Sciences Jülich Centre for Neutron Research (JCNS) Functional Macromolecules and Complexes |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
Please use the identifier: http://dx.doi.org/10.1103/PhysRevB.91.094421 in citations.
We present experimental, numerical, and theoretical evidence for an unusual mode of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering experiments on 8-nm particles of hematite display a loss of diffraction intensity with temperature, the intensity vanishing around 150 K. However, the signal from inelastic neutron scattering remains above that temperature, indicating a magnetic system in constant motion. In addition, the precession frequency of the inelastic magnetic signal shows an increase above 100 K. Numerical Langevin simulations of spin dynamics reproduce all measured neutron data and reveal that thermally activated spin canting gives rise to an unusual type of coherent magnetic precession mode. This “rotor” mode can be seen as a high-temperature version of superparamagnetism and is driven by exchange interactions between the two magnetic sublattices. The frequency of the rotor mode behaves in fair agreement with a simple analytical model, based on a high-temperature approximation of the generally accepted Hamiltonian of the system. The extracted model parameters, such as the magnetic interaction and the axial anisotropy, are in excellent agreement with results from Mössbauer spectroscopy. |