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New Insights about CuO Nanoparticles from Inelastic Neutron Scattering

1
Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
2
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
3
Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA
*
Author to whom correspondence should be addressed.
Nanomaterials 2019, 9(3), 312; https://doi.org/10.3390/nano9030312
Received: 17 January 2019 / Revised: 15 February 2019 / Accepted: 19 February 2019 / Published: 26 February 2019
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Abstract

Inelastic Neutron Scattering (INS) spectroscopy has provided a unique insight into the magnetodymanics of nanoscale copper (II) oxide (CuO). We present evidence for the propagation of magnons in the directions of the ordering vectors of both the commensurate and helically modulated incommensurate antiferromagnetic phases of CuO. The temperature dependency of the magnon spin-wave intensity (in the accessible energy-range of the experiment) conforms to the Bose population of states at low temperatures (T ≤ 100 K), as expected for bosons, then intensity significantly increases, with maximum at about 225 K (close to TN), and decreases at higher temperatures. The obtained results can be related to gradual softening of the dispersion curves of magnon spin-waves and decreasing the spin gap with temperature approaching TN on heating, and slow dissipation of the short-range dynamic spin correlations at higher temperatures. However, the intensity of the magnon signal was found to be particle size dependent, and increases with decreasing particle size. This “reverse size effect” is believed to be related to either creation of single-domain particles at the nanoscale, or “superferromagnetism effect” and the formation of collective particle states. View Full-Text
Keywords: copper oxide; nanoparticles; neutron scattering; magnetism copper oxide; nanoparticles; neutron scattering; magnetism
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Spencer, E.C.; Kolesnikov, A.I.; Woodfield, B.F.; Ross, N.L. New Insights about CuO Nanoparticles from Inelastic Neutron Scattering. Nanomaterials 2019, 9, 312.

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