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Exchange-driven magnetic anomalies in Fe-Zr-B-based nanocomposites

Steer, WA; Forster, GD; Parkin, IP; Roberts, MA; Pankhurst, QA; (2002) Exchange-driven magnetic anomalies in Fe-Zr-B-based nanocomposites. In: HYPERFINE INTERACTIONS. (pp. 223 - 230). KLUWER ACADEMIC PUBL

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Abstract

A series of amorphous Fe-Zr-B-based nanocomposites have been prepared by borohydride chemical reduction. The structural, magnetic and crystallisation properties of these materials have been investigated by Mossbauer spectroscopy, differential scanning calorimetry, X-ray diffraction, EXAFS and SQUID magnetometry. Nanocrystals of iron and iron boride form at ca. 470 degreesC, while the zirconium remains in an amorphous matrix until the samples are heated above 600 degreesC, after which crystalline zirconia is formed. No intermetallic iron-zirconium phases are observed, implying that in the as made state the materials comprise nanocomposites of amorphous iron-boron and amorphous zirconium oxide. Unusually large magnetic coercivities are observed, due to interfacial exchange pinning between the magnetically soft Fe-B nanoparticles and a surface passivation layer. Further magnetic anomalies observed in the heat treated samples indicate the influence of exchange interactions between nanocrystalline grains in an amorphous and insulating matrix.

Type:Proceedings paper
Title:Exchange-driven magnetic anomalies in Fe-Zr-B-based nanocomposites
Event:5th Seeheim Workshop on Mossbauer Spectroscopy
Location:SEEHEIM, GERMANY
Dates:2002-05-21 - 2002-05-25
Keywords:magneto-nanocomposites, magnetic interactions, nanomagnetism, CHEMICAL-REDUCTION, BOROHYDRIDE, ALLOYS
UCL classification:UCL > School of BEAMS > Faculty of Engineering Science > Institute of Biomedical Engineering
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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