Bimagnetic CoO Core/CoFe2O4 Shell Nanoparticles: Synthesis and Magnetic Properties

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• 作者：Enio Lima ; Jr. ; Elin L. Winkler ; Dina Tobia ; Horacio E. Troiani ; Roberto D. Zysler ; Elisabetta Agostinelli ; Dino Fiorani
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：February 14, 2012
• 年：2012
• 卷：24
• 期：3
• 页码：512-516
• 全文大小：322K
• 年卷期：v.24,no.3(February 14, 2012)
• ISSN：1520-5002

文摘

In this work we report on the synthesis, the microstructural characterization, and the magnetic properties of 7 nm bimagnetic core/shell nanoparticles prepared by seed-mediated growth high temperature decomposition of organometallic precursor. The nanoparticles are formed by an antiferromagnetic CoO core coated with ferromagnetic CoFe₂O₄ shell of 2鈥? nm of thickness. XRD and electron diffraction patterns show the reflections of the structure of the CoFe₂O₄ and CoO phases and Dark- and Bright-field TEM images provide evidence of the core鈥搒hell morphology of the system. Magnetic measurements show that the system presents a remarkably large coercivity and high squareness (at 5 K, H_C = 27.8 kOe and M_r/M_S = 0.79), compared to CoFe₂O₄ single phase nanoparticles of comparable size. The enhancement of the effective anisotropy is attributed to the surface and interface exchange coupling effects.

Keywords:

bimagnetic nanoparticles; CoO/CoFe₂O₄ nanoparticles; interface exchange coupling; magnetic anisotropy