Abstract
Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.
Highlights
Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices
To study a single FE nanoparticle morphology and its vortex structure, we designed a composite consisting of BTO nanoparticles and carbon nanoparticles dispersed within a non-ferroelectric polymeric dielectric matrix (Fig. 1, Supplementary Fig. 1 and the Methods section)
By applying an electric field in cycles and monitoring changes in diffraction pattern, we can differentiate BTO nanoparticles acting as nanocapacitor (Supplementary Fig. 3) from the particles which are electrically insulated in dielectric matrix (Supplementary Fig. 4)
Summary
Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Ferroelectric (FE) materials will likely have a broad range of applications in the generation of electronics, such as non-volatile random access memorie (NRAM)[1,2,3,4,5], and energy-storage and battery related technologies[6,7,8] Nanoferroelectrics, unlike their bulk counterparts, show complex topological polarization textures[9], including multi-stable states such as polar vortices[10], which are formed due to long-range interactions mediated by elasticity and electrical boundary conditions. Combining HR-TEM with synchrotron radiation-based reciprocal space mapping has recently permitted the observation of long-range 2D vortex distributions in perovskite superlattices[27] These approaches have not been transferred to direct non-invasive whole-volume studies of vortex structure due to fundamental limitations of the methods, forcing restrictions on studies in the presence of external perturbations, such as applied electric or magnetic fields, and leaving a gap in our understanding of dynamical processes. For a review of advances in imaging of local structure using light sources, see refs 29–34
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