Exchange bias behavior of monodisperse Fe₃O₄/¦Ã-Fe₂O₃ core/shell nanoparticles

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• 作者：Yosun Hwang^a ; S. Angappane^a ; ¹ ; Jongnam Park^b ; Kwangjin An^b ; T. Hyeon^b ; Je-Geun Park^c ; ^d ; ^{jgpark10@snu.ac.kr}
• 关键词：Fe3O4 nanoparticles ; Exchange bias behavior ; Core-shell structure
• 刊名：Current Applied Physics
• 出版年：2012
• 出版时间：May, 2012
• 年：2012
• 卷：12
• 期：3
• 页码：808-811
• 全文大小：512 K

文摘

We have carried out systematic studies on well-characterized monodisperse Fe₃O₄/¦Ã-Fe₂O₃ core/shell nanoparticles of 2-30?nm having a very narrow size distribution and possessing a uniquely mono-layer of surface ¦Ã-Fe₂O₃. This unique core-shell structure, probably having a disordered magnetic surface state, leads us to three key observations of unusual magnetic properties: i) a very large magnetic exchange anisotropy reaching over 7?¡Á?10⁶?erg/cm³ for the smaller particles, ii) exchange bias behavior in the magnetization data of the core/shell Fe₃O₄/¦Ã-Fe₂O₃ nanoparticles, and iii) the temperature dependence of the coercive field following an unusual exponential behavior.