Achieving a high magnetization in sub-nanostructured magnetite films by spin-flipping of tetrahedral Fe3+ cations
magnetite, X-ray magnetic circular dichroism (XMCD), giant magnetization, nanostructured-Fe3O4, ferrite, spin-flipping
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.
Tsinghua University Press
Tun Seng Herng,Wen Xiao,Sock Mui Poh,Feizhou He,Ronny Sutarto,Xiaojian Zhu,Runwei Li,Xinmao Yin,Caozheng Diao,Yang Yang,Xuelian Huang,Xiaojiang Yu,Yuan Ping Feng,Andrivo Rusydi,Jun Ding, Achieving a high magnetization in sub-nanostructured magnetite films by spin-flipping of tetrahedral Fe3+ cations. NanoRes.2015, 8(9): 2935–2945