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Enhanced Magnetoelectric Response and Phonon Abnormality of Self-assembled Feather-like CoFe2O4-BaTiO3 Nanostructures Yu Deng1, 2, Di Wu1, Huiqiang Yu2, Youwei Du1 1 Physics Dept. and Nation. Lab. of Microstructures. , Nanjing Univ., Nanjing, China 2 Center for Modern Analysis, Nanjing Univ., Nanjing, China  ABSTRACT Magnetoelectric (ME) (CoFe2O4)0.3-(BaTiO3)0.7 (CFO-BTO) nanostructures have been synthesized by a combinative using of hydrothermal reaction and polymer-assisted deposition. The feather-like nanostructures have an average diameter of 250nm and lengths up to 5μm, with the single-crystal CFO nanopillars embedded in the BTO matrix. The CFO-BTO nanostructures exhibit good magnetic (Ms=21.0emu/g, Mr=10.4emu/g and Hc=560.7Oe) and ferroelectric properties (Ps=10.5 C/cm2, Pr=5.6 C/cm2), as well as a large ME coefficient of 51.8mV/cmOe. A prominent phonon abnormality has also been detected between 110°C and 140°C. With emphasis on the novel microstructure, the ME response and phonon abnormality of the CFO-BTO nanostructures have been discussed.  INTRODUCTION Multiferroic materials exhibit not only ferroelectricity and magnetism, but also various coupling properties. Recently, they have become more and more attractive because of their potential applications in the multifunctional devices [1-5]. Among them, multiferroic composites made up of piezoelectric and magnetostrictive materials can generate large ME responses at room temperature and low magnetic field, besides their excellent electric and magnetic properties [1,2]. And since the nanostructures can provide more degrees of freedom to optimize the properties, many multiferroic nanostructures have been developed to make use of their excellences [1-5]. However, some problems such as the substrate-clamping effects and the large-scale synthesis are still great challenges. More, the strong coupling effects in them have not been fully understood and become controllable. Therefore, it is still of great value to fabricate novel multiferroic composite nanostructures and explore their size-dependent properties. In this paper, we synthesized feather-like CFO-BTO nanostructures by cost-effective chemical techniques. The CFO-BTO nanostructures show a “pillar-matrix” type self-assembling, with the CFO nanopillars embedded in the BTO matrix. Not only good electric and magnetic properties, but also large ME effect and phonon abnormality have been detected in the nanostructures.

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 EXPERIMENTAL DETAILS The CFO-BTO nanostructures have been prepared through hydrothermal reaction [6] and polymer-assisted deposition [7], as reported in our previous work [8]. Titanate nanofibers are used as starting materials which are synthesized by treating TiO2 in an autoclave with NaOH solution (10M/L) at 150oC for 48h. The titanate nanofibers were hydrothermally treated at 140oC for 7h in a solution of Ba(NO3)2 (0.05M/L) and NaOH (1.0M/L). Then the precipitations were taken out and slowly added into a mixture aqueous solution containing Ba, Ti, Fe and Co cations, which are bound to Pol