Berlin 2018 – scientific programme
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MA: Fachverband Magnetismus
MA 52: Poster II
MA 52.67: Poster
Thursday, March 15, 2018, 15:00–18:00, Poster C
Structural and magnetic properties of Ba2Mg0.4Co1.6Fe12O22 hexaferrites — •B. Georgieva1, S. Kolev1, K. Krezhov2, Ch. Ghelev1, B. Vertruyen3, R. Closset3, A. Mahmoud3, R. Cloots3, A. Zaleski4, and T. Koutzarova1 — 1Institute of Electronics, Bulgarian Academy of Sciences, Sofia, Bulgaria — 2Institute for Nuclear Research and Nuclear Energy, BAS, Sofia, Bulgaria — 3Chemistry Department, University of Liege, Belgium — 4Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
In multiferroic materials, long-range magnetic and ferroelectric orders coexist resulting in a magnetoelectric effect. For example, Y-type hexaferrites, (as Ba2Mg2Fe12O22) have a relatively high temperature of magnetic transition (~200 K) to a spiral spin arrangement and an easy magnetization axis lying in a plane perpendicular to the c crystal axis. Multiferroicity exists without an external magnetic field, a longitudinal-conical spin arrangement arises below 50 K, and the direction of the electric polarization can be controlled by low magnetic fields (<0.02 T). We studied the effect of Co substitution in Ba2Mg2Fe12O22 on its structural and magnetic properties. Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation. Its XRD spectra had the characteristic peaks of the Y-type hexaferrite as a main phase. Less than 2% of CoFe2O4 appeared as a second phase; this was confirmed by Moessbauer spectroscopy. The magnetization at 50kOe was 30emu/g and 26.6emu/g at 4.2 K and 300 K. The ZFC and FC magnetization curves measured at 500 Oe showed a magnetic phase transition from a ferrimagnetic-to-helical spin order at 200 K.