Abstract.From an experimental point of view, room temperature ferroelectricity in BiFeO 3 is raising many questions. Electric measurements made a long time ago on solid-solutions of BiFeO with Pb(Ti,Zr)O been no report of a P(E) (polarization versus electric field) loop at room temperature on single crystals of BiFeO 3. We describe here our procedure to synthesize ceramics and to grow good quality sizeable single crystals by a flux method. We demonstrate that BiFeO 3 is indeed ferroelectric at room-temperature through evidence by Piezoresponse Force Microscopy and P(E) loops. The polarization is found to be large, around 60 μC/cm², a value that has only been reached in thin films. Magnetic measurements using a SQUID magnetometer and Mössbauer spectroscopy are also presented. The latter confirms the results of NMR measurements concerning the anisotropy of the hyperfine field attributed to the magnetic cycloidal structure.

A novel nonaqueous route has been applied for the preparation of nanocrystalline magnetite. In a simple one-pot reaction process, iron(III) acetylacetonate was dissolved in benzyl alcohol and treated in an autoclave between 175 and 200 °C. This approach leads to monocrystalline magnetite particles with sizes ranging from 12 to 25 nm, as evidenced by X-ray analysis, HRTEM, and Raman and Mössbauer spectroscopy. The isolated particles can be redispersed either in polar or nonpolar solvents by coating them just after synthesis with undecanoic acid or dopamine. Simple sedimentation after redispersion in hexane can be used to lower the polydispersity of the sample.

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