Abstract Cobalt ferrite – barium titanate coreshell composite nanoparticles are an important part of the emerging field of magnetoelectric materials. Understanding the structure of these nanoparticles is vital towards controlling and adjusting their key properties for specific applications. Although transmission electron microscopy can reveal nanoparticle size, shape, and crystallinity, key information regarding the magnetic properties and the compositional makeup of the coreshell configuration remains elusive at nanoscale. This paper covers the use of scanning probe microscopy to directly measure these features using topography imaging, magnetic force imaging, and phase imaging. This technique provides significant insights into the intrinsic magnetoelectric coupling between the magnetostrictive cobalt ferrite core and the piezoelectric barium titanate shell. Particularly, this technique was applied to obtain phase images that directly exhibited the coreshell configuration, including an intermediate transition region between the core and the shell. The samples examined include 20 nm and 50 nm cobalt ferrite-barium titanate coreshell nanoparticles fabricated via co-precipitation and sol–gel synthesis. The results revealed a cuboid shape for the cobalt ferrite cores, and an oval shape for the cobalt ferrite-barium titanate coreshell nanoparticles. This result was confirmed by transmission electron microscopy. Additionally, the paper comprehensively analyzes the samples in their powder form via X-ray diffraction. The results indicate that the crystallinity of barium titanate is enhanced as the cobalt ferrite concentration is increased because of heterogeneous nucleation requiring a lower nucleation barrier compared to homogeneous nucleation.

中文翻译：

---

钴铁氧体-钛酸钡核壳磁电纳米粒子的扫描探针显微研究

摘要 铁酸钴-钛酸钡核壳复合纳米粒子是磁电材料新兴领域的重要组成部分。了解这些纳米粒子的结构对于控制和调整其特定应用的关键特性至关重要。尽管透射电子显微镜可以揭示纳米颗粒的大小、形状和结晶度，但在纳米尺度上，关于磁特性和核壳结构的组成构成的关键信息仍然难以捉摸。本文介绍了使用扫描探针显微镜通过地形成像、磁力成像和相位成像直接测量这些特征。该技术提供了对磁致伸缩钴铁氧体核和压电钛酸钡壳之间固有磁电耦合的重要见解。特别是，该技术用于获得直接显示核壳构型的相图像，包括核和壳之间的中间过渡区域。检查的样品包括通过共沉淀和溶胶-凝胶合成制造的 20 nm 和 50 nm 钴铁氧体 - 钛酸钡核壳纳米粒子。结果表明，铁氧体钴核呈长方体形状，铁氧体钴-钛酸钡核壳纳米粒子呈椭圆形。透射电子显微镜证实了这一结果。此外，该论文还通过 X 射线衍射对粉末形式的样品进行了综合分析。