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Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

Brok, Erik; Lefmann, Kim; Deen, Pascale LU ; Lebech, Bente; Jacobsen, Henrik; Nilsen, Goran Jan; Keller, Lukas and Frandsen, Cathrine (2015) In Physical Review B (Condensed Matter and Materials Physics) 91(1).
Abstract
In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed at the particle surfaces and by the broadening of diffraction peaks due to the finite crystallite size. Moreover, the spin structure in magnetic nanoparticles may deviate significantly from that of the corresponding bulk material because of the low-symmetry surroundings of surface atoms and the large relative surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic... (More)
In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed at the particle surfaces and by the broadening of diffraction peaks due to the finite crystallite size. Moreover, the spin structure in magnetic nanoparticles may deviate significantly from that of the corresponding bulk material because of the low-symmetry surroundings of surface atoms and the large relative surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk NiO and platelet-shaped NiO nanoparticles with thickness from greater than 200 nm down to 2.0 nm. The advantage of the applied method is that it is able to clearly separate the structural, the magnetic, and the spin-incoherent scattering signals for all particle sizes. For platelet-shaped particles with thickness from greater than 200 nm down to 2.2 nm we find that the spin orientation deviates about 16 degrees from the primary (111) plane of the platelet-shaped particles. In the smallest particles (2.0 nm thick) we find the spins are oriented with a 30 degrees. average angle to the primary (111) plane of the particles. The results show that polarization analyzed neutron powder diffraction is a viable method to investigate magnetic order in powders of antiferromagnetic nanoparticles. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B (Condensed Matter and Materials Physics)
volume
91
issue
1
publisher
American Physical Society
external identifiers
  • wos:000348473100004
  • scopus:84921801925
ISSN
1098-0121
DOI
10.1103/PhysRevB.91.014431
language
English
LU publication?
yes
id
6e67106a-373a-4cf9-8930-c08364daf0e4 (old id 5201228)
date added to LUP
2015-03-26 13:21:56
date last changed
2017-10-08 03:49:42
@article{6e67106a-373a-4cf9-8930-c08364daf0e4,
  abstract     = {In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed at the particle surfaces and by the broadening of diffraction peaks due to the finite crystallite size. Moreover, the spin structure in magnetic nanoparticles may deviate significantly from that of the corresponding bulk material because of the low-symmetry surroundings of surface atoms and the large relative surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk NiO and platelet-shaped NiO nanoparticles with thickness from greater than 200 nm down to 2.0 nm. The advantage of the applied method is that it is able to clearly separate the structural, the magnetic, and the spin-incoherent scattering signals for all particle sizes. For platelet-shaped particles with thickness from greater than 200 nm down to 2.2 nm we find that the spin orientation deviates about 16 degrees from the primary (111) plane of the platelet-shaped particles. In the smallest particles (2.0 nm thick) we find the spins are oriented with a 30 degrees. average angle to the primary (111) plane of the particles. The results show that polarization analyzed neutron powder diffraction is a viable method to investigate magnetic order in powders of antiferromagnetic nanoparticles.},
  articleno    = {014431},
  author       = {Brok, Erik and Lefmann, Kim and Deen, Pascale and Lebech, Bente and Jacobsen, Henrik and Nilsen, Goran Jan and Keller, Lukas and Frandsen, Cathrine},
  issn         = {1098-0121},
  language     = {eng},
  number       = {1},
  publisher    = {American Physical Society},
  series       = {Physical Review B (Condensed Matter and Materials Physics)},
  title        = {Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO},
  url          = {http://dx.doi.org/10.1103/PhysRevB.91.014431},
  volume       = {91},
  year         = {2015},
}