Magnetic and hyperfine properties of Fe2P nanoparticles dispersed in a porous carbon matrix

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:401

Article

Viali, G. L.¹  Goncalves, G. R.²  Passamani, E. C.¹  Freitas, J. C. C.²  Schettino, M. A., Jr.²  Takeuchi, A. Y.¹  Larica, C.¹ 

[1] Univ Fed Espirito Santo, Dept Phys, Lab Magnetometry & Mossbauer Effect, BR-29075910 Vitoria, ES, Brazil

[2] Univ Fed Espirito Santo, Dept Phys, Lab Carbon & Ceram Mat, BR-29075910 Vitoria, ES, Brazil

关键词: Mossbauer spectroscopy;    Magnetic nanoparticles;    Magnetic;   

DOI  :  10.1016/j.jmmm.2015.10.028

来源: Elsevier

【 摘 要 】

Structural and magnetic properties of nanocomposite, consisting of Fe2P particles dispersed in a porous carbon matrix, have fully been investigated using X-ray diffraction, Mossbauer and ac and dc magnetization measurements. Besides production of the nanocomposite, using an activated carbon (prepared by chemical activation of a char with H3PO4), impregnation with a Fe3+ salt in aqueous medium and subsequent heat treatments under N-2 flow, we found a formation of hexagonal Fe2-xP and orthorhombic FeP in a mass ratio of 4:1, respectively. Low temperature Mossbauer spectra revealed that a large fraction (ca. 28%) of the material is in the paramagnetic state, suggesting that part of the Fe2-xP phase appears in the form of very small particles. A metamagnetic phase transition was also observed for non-stoichiometric Fe2-xP nanoparticles. It is observed at about 150 K, well below the ordering temperature of the Fe2P phase (230 K), and is dependent on the dc-probe fields. Also, the Fe2-xP nanoparticles were found to have a hard-like magnetic character at low temperatures, with coercive field fic of 1.3 KOe. Considering these interesting magnetic and hyperfine properties and also the large specific surface area of the porous carbon matrix, which is not severely reduced after impregnation with the Fe-containing compounds, one may point to promising technological applications of the produced nanocomposite. (C) 2015 Elsevier B.V. All rights reserved.

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