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Microscopic states and the verwey transition of magnetite nanocrystals investigated by nuclear magnetic resonance

Cited 6 time in Web of Science Cited 5 time in Scopus
Authors
Lim, Sumin; Choi, Baeksoon; Lee, Sang Young; Lee, Soonchil; Nahm, Ho-Hyun; Kim, Yong-Hyun; Kim, Taehun; Park, Je-Geun; Lee, Jisoo; Hong, Jaeyoung; Kwon, Soon Gu; Hyeon, Taeghwan
Issue Date
2018-03
Citation
Nano Letters, Vol.18 No.3, pp.1745-1750
Keywords
MagnetitenanocrystalNMRVerwey transitioncharge orderhopping
Abstract
Fe-57 nuclear magnetic resonance (NMR) of magnetite nanocrystals ranging in size from 7 nm to 7 ym is measured. The line width of the NMR spectra changes drastically around 120 K, showing microscopic evidence of the Verwey transition. In the region above the transition temperature, the line width of the spectrum increases and the spin-spin relaxation time decreases as the nanocrystal size decreases. The line-width broadening indicates the significant deformation of magnetic structure and reduction of charge order compared to bulk crystals, even when the structural distortion is unobservable. The reduction of the spin-spin relaxation time is attributed to the suppressed polaron hopping conductivity in ferromagnetic metals, which is a consequence of the enhanced electron-phonon coupling in the quantum-confinement regime. Our results show that the magnetic distortion occurs in the entire nanocrystal and does not comply with the simple model of the core-shell binary structure with a sharp boundary.
ISSN
1530-6984
URI
http://hdl.handle.net/10371/165862
DOI
https://doi.org/10.1021/acs.nanolett.7b04866
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Journal Papers (저널논문_화학생물공학부)
College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Chemical Convergence for Energy and Environment (에너지환경 화학융합기술전공)Journal Papers (저널논문_에너지환경 화학융합기술전공)
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