Structural and magnetic properties of nanosized barium hexaferrite powders obtained by microemulsion techniques

Tatyana I. Koutzarova 1Svetoslav Kolev 1Korneli Grigorov 1Chavdar Ghelev 1Marcel Ausloos 2Tomasz Palewski 4Andrzej J. Zaleski 3Ivan Nedkov 1

1. Institute of Electronics, Bulgarian Academy of Sciences (IE-BAS), 72, Tzarigradsko Chaussee, Sofia 1784, Bulgaria
2. University of Liege, Institute of Physics, SUPRATECS (ULg), B5, Liège 4000, Belgium
3. Polish Academy of Sciences, Institute of Low Temperature and Structure Research (INTiBS), Okólna 2, Wrocław 50-422, Poland
4. 3International Laboratory of High Magnetic Fields and Low Temperatures, Wrocław, Poland

Abstract

The magnetic properties of ferrites are strongly dependent on the chemical composition, the cations distribution and on the preparation method in general, as well as on the structure in particular. It is well known that water-in-oil reverse micelles can be used as microreactors to produce monodispersed nanosized particles. The present work aims to prepare barium hexaferrite (BaFe12O19) powders of nanometer particles size via two types of the microemulsion technique – single microemulsion and double microemulsion. We use a water-in-oil microemulsion system with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, n-butanol as a co-surfactant, n-hexanol as a continuous oil phase, and an aqueous phase. The single microemulsion technique, in which the aqueous phase contains only the Fe3+ and Ba2+ cations is less complicated and much less expensive than the double microemulsion one. The co-precipitation was performed by concentrated solution of NaOH at pH = 12. In the second step of the synthesis, the hydroxide precursor was calcined at 800°C temperature. We were examined the influence of the type of microemulsion techniques on the microstructure, the magneto-crystalline structure, and on the magnetic properties of the barium hexaferrite powders. The microscopy investigations show a narrower grain size distribution and the average particle size is 280 nm, well below the critical mono-domain diameter for BaFe12O19. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The saturation magnetization values (Ms) were obtained from the magnetization curves in high magnetic fields up to 130 kOe. The Ms were determined 43 emu/g and 48.86 emu/g for single and double microemulsion techniques, respectively. The coercive force for the two temperatures was 4.3 kOe and 3 kOe for single and double microemulsion techniques, respectively. The magnetic properties might be related to the mono-domain structure.

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Tatyana I. Koutzarova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 10:05
Revised:   2009-06-07 00:44
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