Development of Novel Multiferroic Composites Based on BaTiO 3 and Hexagonal Ferrites
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1161-I01-06
Development of Novel Multiferroic Composites Based on BaTiO3 and Hexagonal Ferrites D. V. Karpinsky1, E. K Selezneva1, I. K Bdikin1, F. Figueiras1, K. E. Kamentsev2, Y. K Fetisov2, R. C Pullar3, J. Krebbs3, N. M. Alford3, and A. L. Kholkin1 1 Department of Ceramics and Glass Engineering & CICECO, University of Aveiro, Aveiro, 3810-193, Portugal 2 Moscow State Institute of Radioengineering, Electronics and Automation, Moscow, Russia 3 Centre for Physical Electronics and Materials, Department of Materials, Imperial College London, London, UK ABSTRACT New multiferroic composite ceramics with the general formula (x)Ba(Sr)Fe12O19-(1x)BaTiO3 (x=0.1, 0.5) were synthesized via a simple solid-state reaction technique. Crystal structure analysis performed for such materials revealed the presence of two crystalline phases pertinent to the initial composite components. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to assess the crystallinity, microstructure, and local magnetoelectric interactions between ferroelectric and ferromagnetic grains. Magnetic measurements revealed that the saturation magnetization is proportional to the volume fraction of ferrite phase. Dielectric studies demonstrated strong frequency relaxation due to space charge polarization and high conductivity loss making macroscopic magnetoelectric measurements difficult. Novel nanoscale magnetoelectric effect observed by AFM is discussed. INTRODUCTION In the last few years materials which combine ferroelectric and ferromagnetic properties have drawn much attention due to the new physics involved and various potential applications [1-3]. Magnetoelectric (ME) multiferroic materials can change magnetization by applying electric field and vice a versa and thus are useful for microelectronic devices due to the potential for controlling the properties by both electric and magnetic fields. A coexistence of ferromagnetism and ferroelectricity rarely coexists in single-phase materials. The problem is mainly caused by the electronic structure of transition ions in ferroelectric compounds which excludes magnetism. As a result, rare ferroelectric materials with magnetic properties basically have an antiferromagnetic structure with low magnetization and magnetoelectric properties are typically observed at low temperatures. An alternate way to combine magnetism and ferroelectricity is to synthesize the composite materials containing separate magnetic and ferroelectric phases. A number of configurations of these components (particulate, layered, coreshell etc.) can produce remarkable ME effects as recently discussed in the literature [4-7]. In this work, we prepared novel magnetoelectric composites based on barium/strontium hexaferrites and barium titanate and investigated their properties. Barium and strontium hexagonal ferrites (abbreviated as BaM and SrM, respectively) have found various applications in the past as a material of choice for permanent magnets and storage media. On the other hand, barium
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