Abstract

Multiferroic materials, in which long-range magnetic and ferroelectric orders coexist, have recently been of great interest in the fields of both basic and applied sciences. The Y-type hexagonal ferrite Ba2Mg2Fe12O22 is an example of a multiferroic material. Its single crystals have a relatively high spiral-magnetic transition temperature (~200 K), show multiferroic properties at zero magnetic field, and the direction of the ferroelectric polarization can be controlled by a weak magnetic field (< 0.02 T) [1]. We present a study of the influence of substituting the Mg2+ cations in the Y-type Ba2Mg2Fe12O22 hexaferrites with a magnetic cation, such as Co2+, on the structural and magnetic properties. The Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation. High-power ultrasound was applied to assist the co-precipitation process. The precursors produced were synthesized at 1170°С. The XRD spectra of the powders showed the characteristic peaks corresponding to the Y-type hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2%) as second phase. This was also confirmed by Mössbauer spectroscopy measurements. The magnetization values at 50 kOe were 30 emu/g and 26.6 emu/g at 4.2 and 300 K, respectively. The ZFC and FC magnetization curves were obtained at a magnetic field of 500 Oe. The magnetic measurements revealed a magnetic phase transition at 200 K from ferrimagnetic-to-helical spin order. Such a transition is considered as a precondition for the material to exhibit multiferroic properties. [1] K. Taniguchi, N. Abe, S. Ohtani, H. Umetsu, T. Arima, "Ferroelectric polarization reversal by a magnetic field in multiferroic Y-type hexaferrite Ba2Mg2Fe12O22", Appl. Phys. Express, vol. 1, art. num. 031301, 2008.

Highlights

  • Multiferroic materials form a special class of magnetic materials

  • In our previous studies [10, 11] we showed that in a Ba2Mg2Fe12O22 powder material synthesized by sonochemical co-precipitation the magnetic phase transition from ferromagnetic-to-spiral spin order occurs at 196 K at a magnetic field of 100 Oe

  • The X-ray diffraction (XRD) result showed the characteristic peaks corresponding to the Y-type hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2 %) as a negligible second phase

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Summary

Introduction

Multiferroic materials form a special class of magnetic materials. Long-range magnetic and ferroelectric orders coexist, a property that has provoked keen researchers’ interest from both basic and practical points of view [1, 2]. The magneto-electric multiferroics are materials that combine coupled electric and magnetic dipoles [3]. Research in the past decade has demonstrated that magneto-electric effect can be induced by complex internal arrangements of magnetic moments in some hexaferrites. One of the first magnetoelectric hexaferrites discovered was Ba2Mg2Fe12O22. It has a relatively high spiral-magnetic transition temperature (~200 K), shows multiferroic properties at zero magnetic field and the direction of the electric polarization can be governed by relatively low magnetic fields (

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