Journal article
Magnetic fluctuations in nanosized goethite (alpha-FeOOH) grains
Department of Physics, Technical University of Denmark1
Center for Electron Nanoscopy, Technical University of Denmark2
University of Cambridge3
University of Copenhagen4
Magnetic Systems Group, LabChip Section, Department of Micro- and Nanotechnology, Technical University of Denmark5
LabChip Section, Department of Micro- and Nanotechnology, Technical University of Denmark6
Department of Micro- and Nanotechnology, Technical University of Denmark7
Quantum Physics and Information Technology, Department of Physics, Technical University of Denmark8
Center for Nanoteknologi, Centers, Technical University of Denmark9
Mossbauer spectra of antiferromagnetic goethite (alpha-FeOOH) particles usually show an asymmetric line broadening, which increases with increasing temperature, although the magnetic anisotropy is expected to be so large that magnetic relaxation effects should be negligible. By use of high resolution transmission electron microscopy we have studied a sample of goethite particles and have found that the particles contain many defects such as low angle grain boundaries, in accordance with previous studies of other samples of goethite particles.
Such defects can result in a magnetic mismatch at the grain boundaries between nanometer-sized grains, leading to a weakened magnetic coupling between the grains. We show that the Mossbauer data of goethite can be explained by fluctuations of the sublattice magnetization directions in such weakly coupled grains.
It is likely that the influence of defects such as low angle grain boundaries also plays a role with regards to the magnetic properties in other antiferromagnetic nanograin systems. We discuss the results in relation to Mossbauer studies of alpha-Fe2O3 and alpha-Fe2O3/NiO nanoparticles.
Language: | English |
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Year: | 2009 |
Pages: | 016007 |
ISSN: | 1361648x and 09538984 |
Types: | Journal article |
DOI: | 10.1088/0953-8984/21/1/016007 |
ORCIDs: | Hansen, Mikkel Fougt and Frandsen, Cathrine |