Becker, Klaus-Dieter

Da Silva, Klebson L.

Feldhoff, Armin

Litterst, Fred Jochen

Menzel, Dirk

Paesano, Andrea

Šepelák, Vladimir

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Enhanced magnetization in pre-nanocrystalline BiFeO 3 prepared by mechanosynthesis

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diffusion-fundamentals   The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application www.diffusion-fundamentals.org, ISSN 1862-4138; © 2005-2010   Diffusion Fundamentals 12 (2010) 78  © K. L. da Silva Enhanced Magnetization in Pre-Nanocrystalline BiFeO3 Prepared by Mechanosynthesis K. L. Da Silva,*,1,2 D. Menzel,3 A. Feldhoff,4 A. Paesano Jr.,2 V. Šepelák,5 F. J. Litterst,3  K.-D. Becker 2  1 Braunschweig University of Technology, Institute of Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig, Germany  2 State University of Maringá, Department of Physics, Av. Colombo, 5790,  87020-900 Maringá Brazil 3 Braunschweig University of Technology, Institute of Condensed Matter Physics,  Mendelssohnstr. 2-3, 38106 Braunschweig, Germany 4 Leibniz University Hannover, Institute of Physical Chemistry and Electrochemistry, Callinstr. 3a, 30167 Hannover, Germany 5 Karlsruhe Institute of Technology, Institute of Nanotechnology,  Hermann-von-Helmholtz-Platz 1, 76347 Eggenstein-Leopoldshafen, Germany  E-Mail: lucenildodasilva@yahoo.com.br  Presented at the Bunsen Colloquium: Spectroscopic Methods in Solid State Diffusion and Reactions September 24th − 25th, 2009, Leibniz University Hannover, Germany   Multiferroics are promising materials for the design and synthesis of multifunctional materials. They are noteworthy for their unique and strong coupling of electric, magnetic, and structural order parame-ters, giving rise to simultaneous ferroelectricity, ferromagnetism, and ferroelasticity [1]. BiFeO3 (BFO) is one of the most studied multiferroics, exhibiting antiferromagnetic and ferroelectric proper-ties at room temperature [2]. In spite of intense study, a fundamental understanding of structure-property correlations in BiFeO3 is still lacking. Specifically, the fundamental dependence of its mag-netic behavior on the particle size is an issue of interest.  In the present work, a one–step synthesis of BFO prepared via mechanochemical processing of the α-Fe2O3/Bi2O3 mixture at room temperature is reported. The mechanically induced phase evolution of the mixture is followed by XRD (Fig. 1) and 57Fe Mössbauer spectroscopy (Fig. 2). It was revealed that the mechanosynthesis of BFO phase is completed after 12 h. Compared to the traditional synthesis (ceramic) route to BFO, the mechanochemical process used here represents a one-step, high-yield, low-temperature and low-cost procedure for the synthesis of BFO. High-resolution TEM studies revealed the nanocrystalline nature of the mechanosynthesized fer-rite. The rhombohedral structure of the as-prepared BFO with space group R3c was refined using Rietveld method. Mössbauer spectroscopy revealed the superparamagnetic state of the nanocrystalline ferrite at room temperature. Quantitative information on the short-range structure, provided by the nuclear spectroscopic technique, is complemented by the investigation of the magnetic behavior (SQUID measurements) of mechanochemically prepared BFO on a macroscopic scale. The saturation magnetization of the me-chanosynthesized BFO is compared with that of the bulk material prepared by the conventional syn-Da Silva et al., Enhanced Magnetization in Pre-Nanocrystalline BiFeO3  diffusion-fundamentals    www.diffusion-online.org  Diffusion Fundamentals 12 (2010) 79  © K. L. da Silva thesis method. An attempt is made to find correlations between the structural disorder and magnetic behavior of mechanosynthesized BFO.     Fig. 1  X-ray diffraction of Fe2O3/Bi2O3 milled for: 0.25 h, 4 h, 8 h and 12 h.      Fig. 2 Mössbauer spectra of BiFeO3 prepared by ball milling of the Bi2O3/Fe2O3 mixture for: 15 min, 4 h, 8 h and 12 h.  Acknowledgement. The present work was supported by the DFG. References [1] T.-J. Park, G. C. Papaefthymiou, A. J. Viescas, A. R. Moodenbaugh, S. S. Wong, Nano Lett. 7 (2007) 766. [2] Y. Yang, J. Y. Sun, K. Zhu, Y. L. Liu, J. Chen and X. R. Xing, Physica B 404 (2009) 171. 

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Enhanced magnetization in pre-nanocrystalline BiFeO 3 prepared by mechanosynthesis

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