Carbon encapsulation of magnetite nanoparticles enhances magnetism at room-temperature due to spin-polarized charge transfer

This study fabricated amorphous-carbon-encapsulated magnetite (Fe3O4@a-C) nanoparticles (NPs) and observed that the encapsulation significantly enhanced the room-temperature magnetization of the NPs by approximately 22.5%. Generalized gradient approximation with the Hubbard-U correction involved the...

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Bibliographic Details
Published in:Applied physics letters 2021-02, Vol.118 (7)
Main Authors: Lee, Jiann-Shing, Wu, Wen-Bin, Chen, Jiunn, Chen, Chi-Liang, Kuo, Hung-Wei, Lin, Chun-Rong, Lin, Hong-Ji, Chen, Chien-Te
Format: Article
Language:English
Subjects:
Applied physics
Carbon
Charge transfer
Dichroism
Encapsulation
Finite element method
Ion charge
Iron oxides
Magnetism
Magnetite
Nanoparticles
Reduction
Room temperature
Spectrum analysis
Synchrotron radiation
Synchrotrons
X ray absorption
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Summary:This study fabricated amorphous-carbon-encapsulated magnetite (Fe3O4@a-C) nanoparticles (NPs) and observed that the encapsulation significantly enhanced the room-temperature magnetization of the NPs by approximately 22.5%. Generalized gradient approximation with the Hubbard-U correction involved the ionic picture hypothesis of electron acceptors for Fe3O4, namely, e2↓ t23↓ → e2↓ t23↓ e↑, which link the spin-polarized charge transfer to Fe ions at the tetrahedral site FeA of Fe3O4. Fe K-edge X-ray absorption near-edge structure (XANES) spectra suggested a formal charge reduction in the FeA of the Fe3O4@a-C NPs. Moreover, Fe L3-edge x-ray magnetic circular dichroism yielded the same conclusion as that obtained using the XANES spectra and suggested the restoration of an orbital moment in the Fe3O4@a-C NPs. Synchrotron radiation spectroscopy confirmed the charge reduction of FeA, which accounted for the magnetic enhancement.
ISSN:0003-6951
1077-3118
DOI:10.1063/5.0036861