Size Distribution and Frustrated Antiferromagnetic Coupling Effects on the Magnetic Behavior of Ultrafine Akagan茅ite (尾-FeOOH) Nanoparticles

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• 作者：Carlos Luna ; Maxim Ilyn ; V铆ctor Vega ; V铆ctor M. Prida ; Juli谩n Gonz谩lez ; Raquel Mendoza-Res茅ndez
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 11, 2014
• 年：2014
• 卷：118
• 期：36
• 页码：21128-21139
• 全文大小：684K
• ISSN：1932-7455

文摘

The magnetic properties of low dimensional materials of several iron oxyhydroxide phases, such as akagan茅ite (尾-FeOOH) or lepidocrocite (纬-FeO(OH)), remain poorly explored, probably due to their specific preparation as single crystalline phase requires special conditions owing to their structural instability. In the present work, ultrafine akagan茅ite nanoparticles were prepared by the hydrolysis of FeCl₃ solutions at room temperature induced by the presence of NaOH. The resulting product was characterized by several analytical techniques. Structural investigations using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) revealed that the sample was mainly constituted by rather-equiaxial akagan茅ite nanocrystals with mean diameter of 3.3 卤 0.5 nm. In addition, a small amount of rodlike akagan茅ite particles with 23 卤 5 nm in length and 5 卤 1 nm in width was also detected. The study of the respective dependences of the dc magnetization and the ac susceptibility on temperature and exciting magnetic field revealed complex magnetic relaxation processes, high coercivity values at low temperature, and exchange bias effect. These results have been tentatively explained considering size distribution effects and the presence of superparamagnetic and spin glass-like contributions arising from the frustration of the antiferromagnetic order owing to surface effects and an insufficient filling of the akagan茅ite channels with Cl^{鈥?/sup> anions.}