The magnetization reversal in CoFe₂O₄/CoFe₂ granular systems

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• 作者：J. Jin ; X. Sun ; M. Wang ; Z.L. Ding ; Y.Q. Ma
• 关键词：CoFe2O4/CoFe2 ; Reentrant spin ; glass ; Exchange–spring ; Dipolar interaction ; Magnetic properties ; Nanocomposites
• 刊名：Journal of Nanoparticle Research
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：18
• 期：12
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Nanotechnology; Inorganic Chemistry; Characterization and Evaluation of Materials; Physical Chemistry; Optics, Lasers, Photonics, Optical Devices;
• 出版者：Springer Netherlands
• ISSN：1572-896X
• 卷排序：18

文摘

The temperature-dependent field cooling (FC) and zero-field cooling (ZFC) magnetizations, i.e., M_FC and M_ZFC, measured under different magnetic fields from 500 Oe to 20 kOe have been investigated on two exchange–spring CoFe₂O₄/CoFe₂ composites with different relative content of CoFe₂. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at a field-dependent irreversible temperature T_irr. For the sample with less CoFe₂, the curves of −d(M_FC − M_ZFC)/dT versus temperature T exhibit a broad peak at an intermediate temperature T₂ below T_irr, and the moments are suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the −d(M_FC − M_ZFC)/dT curves of the sample with more CoFe₂, besides a broad peat at an intermediate temperature T₂, a rapid rise around the low temperature T₁~15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T₂ and T_irr towards a lower temperature, and the shift of T₂ is attributable to the moment reversal of CoFe₂O₄.