Nucleation-Induced Self-Assembly of Multiferroic BiFeO₃–CoFe₂O₄ Nanocomposites

Large areas of perfectly ordered magnetic CoFe₂O₄ nanopillars embedded in a ferroelectric BiFeO₃ matrix were successfully fabricated via a novel nucleation-induced self-assembly process. The nucleation centers of the magnetic pillars are induced before the growth of the composite structure using anodic aluminum oxide (AAO) and lithography-defined gold membranes as hard mask. High structural quality and good functional properties were obtained. Magneto-capacitance data revealed extremely low losses and magneto-electric coupling of about 0.9 μC/cmOe. The present fabrication process might be relevant for inducing ordering in systems based on phase separation, as the nucleation and growth is a rather general feature of these systems

First-Order Reversal Curve Probing of Spatially Resolved Polarization Switching Dynamics in Ferroelectric Nanocapacitors

Spatially resolved polarization switching in ferroelectric nanocapacitors was studied on the sub-25 nm scale using the first-order reversal curve (FORC) method. The chosen capacitor geometry allows both high-veracity observation of the domain structure and mapping of polarization switching in a uniform field, synergistically combining microstructural observations and probing of uniform-field polarization responses as relevant to device operation. A classical Kolmogorov–Avrami–Ishibashi model has been adapted to the voltage domain, and the individual switching dynamics of the FORC response curves are well approximated by the adapted model. The comparison with microstructures suggests a strong spatial variability of the switching dynamics inside the nanocapacitors