Magnetic properties of nano-scale hematite, α-Fe{sub 2}O{sub 3}, studied by time-of-flight inelastic neutron spectroscopy

Journal Article · Tue Jan 28 00:00:00 EST 2014 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4862235· OSTI ID:22255209

Hill, Adrian H. ^[1]; Jacobsen, Henrik; Holm, Sonja L.; Lefmann, Kim ^[2]; Stewart, J. Ross ^[3]; Jiao, Feng ^[4]; Jensen, Niels P. ^[5]; Mutka, Hannu; Seydel, Tilo ^[6]; Harrison, Andrew ^[6]

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1. The European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex 9 (France)
2. Nanoscience Centre, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen (Denmark)
3. Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 OQX (United Kingdom)
4. Department of Chemical Engineering, University of Delaware, Center for Catalytic Science and Technology, 150 Academy Street, Newark, Delaware 19716-3110 (United States)
5. Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)
6. The Institute Laue-Langevin, 6 rue Jules Horowitz, BP156, 38042 Grenoble Cedex 9 (France)

Samples of nanoscale hematite, α-Fe{sub 2}O{sub 3}, with different surface geometries and properties have been studied with inelastic time-of-flight neutron scattering. The 15 nm diameter nanoparticles previously shown to have two collective magnetic excitation modes in separate triple-axis neutron scattering studies have been studied in further detail using the advantage of a large detector area, high resolution, and large energy transfer range of the IN5 TOF spectrometer. A mesoporous hematite sample has also been studied, showing similarities to that of the nanoparticle sample and bulk α-Fe{sub 2}O{sub 3}. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ{sub 1}. This is shown to remain negative throughout the temperature range studied in both samples, providing an explanation for the previously observed suppression of the Morin transition in the mesoporous material. The values of this anisotropy coefficient are found to lie between those of bulk and nano-particulate samples, showing the hybrid nature of the mesoporous 3-dimensional structure.

• OSTI ID: 22255209
• Journal Information: Journal of Chemical Physics, Vol. 140, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANISOTROPY
ENERGY TRANSFER
EXCITATION
FERRITES
HEMATITE
IRON OXIDES
MAGNETIC PROPERTIES
NANOSTRUCTURES
NEUTRON DIFFRACTION
NEUTRON SPECTROSCOPY
PARTICLES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE