Scanning probe microscopy study of cobalt ferrite-barium titanate coreshell magnetoelectric nanoparticles

[摘要] 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.

[发布日期] 2020-12-15

[关键词] Coreshell nanoparticles;Nanoparticle characterization;Scanning probe microscopy;Magnetoelectricity;Lattice distortion