Magnetic properties of nano-scale hematite, α-Fe2O3, studied by time-of-flight inelastic neutron spectroscopy

Adrian H. Hill, Henrik Skåret Jacobsen, J. Ross Stewart, Feng Jiao, Niels P. Jensen, Sonja L. Holm, Hannu Mutka, Tilo Seydel, Andrew Harrison, Kim Lefmann

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Abstract

Samples of nanoscale hematite, α-Fe2O3, 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-Fe2O3. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ1. 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.

Original languageEnglish
Article number044709
JournalJournal of Chemical Physics
Volume140
Issue number4
Number of pages8
ISSN0021-9606
DOIs
Publication statusPublished - 2014

Cite this

Hill, A. H., Jacobsen, H. S., Stewart, J. R., Jiao, F., Jensen, N. P., Holm, S. L., Mutka, H., Seydel, T., Harrison, A., & Lefmann, K. (2014). Magnetic properties of nano-scale hematite, α-Fe2O3, studied by time-of-flight inelastic neutron spectroscopy. Journal of Chemical Physics, 140(4), [044709]. https://doi.org/10.1063/1.4862235