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Open Access Nano Express

Magnetoelectricity in CoFe2O4 nanocrystal-P(VDF-HFP) thin films

Xiaohua Liu123, Shuangyi Liu124, Myung-Geun Han5, Lukas Zhao6, Haiming Deng6, Jackie Li4, Yimei Zhu5, Lia Krusin-Elbaum6 and Stephen O’Brien123*

Author affiliations

1 Department of Chemistry, The City College of New York, Marshak-1326, 160 Convent Ave, New York, NY 10031, USA

2 Energy Institute, The City University of New York, New York, NY 10031, USA

3 Department of Chemistry, The Graduate Center of CUNY, New York, NY 10016, USA

4 Department of Mechanical Engineering, The City College of New York, Marshak-1326, 160 Convent Ave, New York, NY 10031, USA

5 Department of Material Science and Condensed Matter Physics, Brookhaven National Laboratory, Building 480, Upton, NY 11973, USA

6 Department of Physics, The City College of New York, 160 Convent Ave, New York, NY 10031, USA

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Citation and License

Nanoscale Research Letters 2013, 8:374  doi:10.1186/1556-276X-8-374

Published: 3 September 2013

Abstract

Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe2O4 polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (Ms). An enhancement of the effective permittivity and saturation magnetization of the CoFe2O4-P(VDF-HFP) films was observed and directly compared with CoFe2O4-polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe2O4-P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of Ms up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe2O4-P(VDF-HFP) sample.

Keywords:
Thin film; Magnetoelectric nanocomposite; Magnetostrictive; P(VDF-HFP); CoFe2O4