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Nano Research

Article Title

Achieving a high magnetization in sub-nanostructured magnetite films by spin-flipping of tetrahedral Fe3+ cations

Authors

Tun Seng Herng, Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 119260, Singapore Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
Wen Xiao, Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 119260, Singapore
Sock Mui Poh, Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore NUSNNI-Nanocore, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
Feizhou He, Canadian Light Source, Saskatoon, Saskatchewan, S7N 2V3, Canada
Ronny Sutarto, Canadian Light Source, Saskatoon, Saskatchewan, S7N 2V3, Canada
Xiaojian Zhu, Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Ningbo 315201, China
Runwei Li, Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Ningbo 315201, China
Xinmao Yin, Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore NUSNNI-Nanocore, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
Caozheng Diao, Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
Yang Yang, Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 119260, Singapore
Xuelian Huang, Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 119260, Singapore
Xiaojiang Yu, Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
Yuan Ping Feng, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
Andrivo Rusydi, Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore NUSNNI-Nanocore, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
Jun Ding, Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 119260, Singapore

Keywords

magnetite, X-ray magnetic circular dichroism (XMCD), giant magnetization, nanostructured-Fe3O4, ferrite, spin-flipping

Abstract

Magnetite Fe3O4 (ferrite) has attracted considerable interest for its exceptional physical properties: It is predicted to be a semimetallic ferromagnetic with a high Curie temperature, it displays a metal-insulator transition, and has potential oxide-electronics applications. Here, we fabricate a high-magnetization (> 1 Tesla) high-resistance (~0.1 Ω·cm) sub-nanostructured (grain size < 3 nm) Fe3O4 film via grain-size control and nano-engineering. We report a new phenomenon of spinflipping of the valence-spin tetrahedral Fe3+ in the sub-nanostructured Fe3O4 film, which produces the high magnetization. Using soft X-ray magnetic circular dichroism and soft X-ray absorption, both at the Fe L3,2- and O K-edges, and supported by first-principles and charge-transfer multiple calculations, we observe an anomalous enhancement of double exchange, accompanied by a suppression of the superexchange interactions because of the spin-flipping mechanism via oxygen at the grain boundaries. Our result may open avenues for developing spinmanipulated giant magnetic Fe3O4-based compounds via nano-grain size control.

Graphical Abstract

Publisher

Tsinghua University Press

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