Reversible Manipulation of Polar Topologies in Oxide Ferroelectrics via Electric Fields.

Polar topologies show great potentials in memories and other nano-micro devices. To integrate with silicon conducting circuits, it is vital to understand the dynamic evolution and the transformation of different domain configurations under external stimulus. Here in situ transmission electron microscopy is performed and the electrically controlled creation and annihilation of large-scale polar flux-closure array from typical c/a domains in PbTiO/SrTiO bilayers is directly observed.

A Roadmap for Ferroelectric-Antiferroelectric Phase Transition.

Antiferroelectric materials have shown great potential in electronic devices benefiting from the reversible phase transition between ferroelectric and antiferroelectric phases. Understanding the dipole arrangements and clear phase transition pathways is crucial for design of antiferroelectric materials-based energy storage and conversion devices. However, the specific phase transition details remain largely unclear and even controversial to date.

Polar Bloch points in strained ferroelectric films.

Topological domain structures have drawn great attention as they have potential applications in future electronic devices. As an important concept linking the quantum and classical magnetism, a magnetic Bloch point, predicted in 1960s but not observed directly so far, is a singular point around which magnetization vectors orient to nearly all directions. Here we show polar Bloch points in tensile-strained ultrathin ferroelectric PbTiO films, which are alternatively visualized by phase-field simulations and aberration-corrected scanning transmission electron microscopic imaging.

Room-Temperature Ferroelectricity of Paraelectric Oxides Tailored by Nano-Engineering.

Inducing clear ferroelectricity in the quantum paraelectric SrTiO is important for triggering methods to discover hidden phases in condensed matter physics. Several methods such as isotope substitution and freestanding membranes could introduce ferroelectricity in SrTiO toward nonvolatile memory applications. However, the stable transformation from quantum paraelectric SrTiO to ferroelectricity SrTiO at room temperature still remains challenging.

Achieving High-Temperature Multiferroism by Atomic Architecture.

Materials with multiple order parameters, typically, in which ferroelectricity and magnetism are coupled, are illuminative for next-generation multifunctional electronics. However, searching for such single-phase multiferroics is challenging owing to antagonistic orbital occupancy and chemical bonding requirements for polarity and magnetism. Appropriate multiferroic candidates have been proposed, but their practical implementation is impeded by the low working temperature, weak coupling between ferroic orders, or antiparallel spin alignment in magnetic sublattices.

Real-Time Transformation of Flux-Closure Domains with Superhigh Thermal Stability.

Polar topologies have received extensive attention due to their exotic configurations and functionalities. Understanding their responsive behaviors to external stimuli, especially thermal excitation, is highly desirable to extend their applications to high temperature, which is still unclear. Here, combining transmission electron microscopy and phase-field simulations, the thermal dynamics of the flux-closure domains were illuminated in PbTiO/SrTiO multilayers.

Polar Magnetism Above 600 K with High Adaptability in Perovskite Oxides.

High magnetic order temperature, sustainable polar insulating state, and tolerance to device integrations are substantial advantages for applications in next-generation spintronics. However, engineering such functionality in a single-phase system remains a challenge owing to the contradicted chemical and electronic requirements for polar nature and magnetism, especially with an ordering state highly above room temperature. Perovskite-related oxides with unique flexibility allow electron-unpaired subsystems to merge into the polar lattice to induce magnetic interactions, combined with their inherent asymmetry, thereby promising polar magnet design.

Magneto-Electric-Optical Coupling in Multiferroic BiFeO -Based Films.

Manipulating ferroic orders and realizing their coupling in multiferroics at room temperature are promising for designing future multifunctional devices. Single external stimulation has been extensively proved to demonstrate the ability of ferroelastic switching in multiferroic oxides, which is crucial to bridge the ferroelectricity and magnetism. However, it is still challenging to directly realize multi-field-driven magnetoelectric coupling in multiferroic oxides as potential multifunctional electrical devices.

Thickness-Dependent Polar Domain Evolution in Strained, Ultrathin PbTiO Films.

Ferroelectric ultrathin films have great potential in electronic devices and device miniaturization with the innovation of technology. In the process of product commercialization, understanding the domain evolution and topological properties of ferroelectrics is a prerequisite for high-density storage devices. In this work, a series of ultrathin PbTiO (PTO) films with varying thicknesses were deposited on cubic KTaO substrates by pulsed laser deposition and were researched by Cs-corrected scanning transmission electron microscopy (STEM), reciprocal space mapping (RSM), and piezoresponse force microscopy (PFM).

Atomic mapping of periodic dipole waves in ferroelectric oxide.

A dipole wave is composed of head-to-tail connected electric dipoles in the form of sine function. Potential applications in information carrying, transporting, and processing are expected, and logic circuits based on nonlinear wave interaction are promising for dipole waves. Although similar spin waves are well known in ferromagnetic materials for their roles in some physical essence, electric dipole wave behavior and even its existence in ferroelectric materials are still elusive.

Spinodal Decomposition-Driven Endurable Resistive Switching in Perovskite Oxides.

Common pursuits of developing nanometric logic and neuromorphic applications have motivated intensive research studies into low-dimensional resistive random-access memory (RRAM) materials. However, fabricating resistive switching medium with inherent stability and homogeneity still remains a bottleneck. Herein, we report a self-assembled uniform biphasic system, comprising low-resistance 3 nm-wide (Bi,La)FeO nanosheets coherently embedded in a high-resistance (Bi,La)FeO matrix, which were spinodally decomposed from an overall stoichiometry of the (Bi,La)FeO parent phase, as a promising nanocomposite to be a stable and endurable RRAM medium.

[Pollution Characteristics of Water-soluble Inorganic Ions in Chengdu in Summer and Winter].

The water-soluble inorganic ions (WSIIs) in PM and gaseous precursors of Chengdu were continuously observed by a gas and aerosol collector combined with ion chromatography (GAC-IC) in the summer and winter of 2017, and both their pollution characteristics and a typical pollution process in winter were analyzed. It was found that the concentration of PM in winter (100.2 μg·m) was significantly higher than that in summer (34.