Spin waves across three-dimensional, close-packed nanoparticles

Inelastic neutron scattering is utilized to directly measure inter-nanoparticle spin waves, or magnons, which arise from the magnetic coupling between 8.4 nm ferrite nanoparticles that are self-assembled into a close-packed lattice, yet are physically separated by oleic acid surfactant. The resultin...

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Bibliographic Details
Published in:New journal of physics 2018-12, Vol.20 (12), p.123020
Main Authors: Krycka, Kathryn L, Rhyne, James J, Oberdick, Samuel D, Abdelgawad, Ahmed M, Borchers, Julie A, Ijiri, Yumi, Majetich, Sara A, Lynn, Jeffrey W
Format: Article
Language:English
Subjects:
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Close packed lattices
Dispersion curve analysis
Energy gap
Inelastic scattering
Magnons
Nanoparticles
Neutron scattering
Neutrons
Oleic acid
Physics
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Self-assembly
Temperature dependence
Three dimensional models
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Summary:Inelastic neutron scattering is utilized to directly measure inter-nanoparticle spin waves, or magnons, which arise from the magnetic coupling between 8.4 nm ferrite nanoparticles that are self-assembled into a close-packed lattice, yet are physically separated by oleic acid surfactant. The resulting dispersion curve yields a physically-reasonable, non-negative energy gap only when the effective Q is reduced by the inter-particle spacing. This Q renormalization strongly indicates that the dispersion is a collective excitation between the nanoparticles, rather than originating from within individual nanoparticles. Additionally, the observed magnons are dispersive, respond to an applied magnetic field, and display the expected temperature-dependent Bose population factor. The experimental results are well explained by a limited parameter model which treats the three-dimensional ordered, magnetic nanoparticles as dipolar-coupled superspins.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/aaef17