Department of Chemistry, The City College of New York, Marshak-1326, 160 Convent Ave, New York, NY 10031, USA.
Nanoscale Res Lett. 2013 Sep 3;8(1):374. doi: 10.1186/1556-276X-8-374.
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.
过渡金属铁氧体，如 CoFe2O4，具有较大的磁致伸缩系数和较高的居里温度（Tc > 600 K），是在纳米尺度上产生磁有序的优秀候选材料，并为制造具有优化磁电耦合潜力的均匀颗粒-基体薄膜提供了途径。在这里，我们通过多次旋涂和浇铸制备了一系列由亚铁磁性钴铁氧体纳米晶体（8 至 18 nm）和铁电/压电聚合物聚（偏二氟乙烯-共-六氟丙烯），P(VDF-HFP)组成的 0-3 型纳米复合薄膜，厚度范围为 200nm 至 1.6 μm。我们通过 XRD、TEM、HRTEM、STEM 和 SEM 描述了纳米晶体和复合薄膜的合成和结构表征，以及介电和磁性能，以确定两相之间协同相互作用的证据。CoFe2O4 聚合物纳米复合薄膜表现出与组成相关的有效介电常数、损耗角正切和特定饱和磁化强度（Ms）。观察到 CoFe2O4-P(VDF-HFP)薄膜的有效介电常数和饱和磁化强度增强，并与通过相同方法制备的非铁电聚合物基纳米复合材料 CoFe2O4-聚乙烯基吡咯烷酮进行了直接比较。比较结果为 CoFe2O4-P(VDF-HFP)中观察到磁电效应提供了证据，这归因于磁致伸缩/压电相互作用。在 10wt% CoFe2O4-P(VDF-HFP)样品中，室温下观察到 Ms 增强了+20.7%。
