Structural instability of <scp>ZnFe₂O₄</scp>‐<scp>BaTiO₃</scp> magnetoelectric core‐shell nanoparticle: An in situ analysis by <scp>PFM</scp>

Abstract Magnetoelectric core‐shell nanoparticles (ME CSNPs) have gained significant attention for their potential applications in multifunctional devices. We investigate the electrical stability of ZnFe 2 O 4 ‐BaTiO 3 ME CSNPs (ZFO‐BTO ME CSNPs) under various external bias voltages. The phase composition of the core‐shell nanoparticles was determined through Rietveld refinement of X‐ray diffraction data, indicating a tetragonal BaTiO 3 shell and cubic ZnFe 2 O 4 core, present in a weight ratio of 63.63:35.20. Transmission electron microscopy (TEM) analysis shows that the core is composed of ZnFe 2 O 4 with a diameter of 30–50 nm, surrounded by a BaTiO 3 shell with a diameter ranging from 100 to 400 nm. Piezoresponse force microscopy (PFM) results demonstrate that ZFO‐BTO CSNPs exhibit a stable core‐shell configuration up to 1 V, beyond which structural disintegration occurs. The instability of ZFO‐BTO ME CSNPs is attributed to nonuniform interfacial strain, low ZnFe 2 O 4 core magnetostriction, and a suboptimal core‐to‐shell thickness ratio. PFM switching studies reveal 90° domain polarization in the BaTiO 3 shell. These findings provide valuable insights into the design of novel core‐shell nanocomposites with enhanced magnetoelectric coupling and structural stability.