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.

Large Polarization Near 50 μC/cm in a Single Unit Cell Layer SrTiO.

The generally nonpolar SrTiO has attracted more attention recently because of its possibly induced novel polar states and related paraelectric-ferroelectric phase transitions. By using controlled pulsed laser deposition, high-quality, ultrathin, and strained SrTiO layers were obtained. Here, transmission electron microscopy and theoretical simulations have unveiled highly polar states in SrTiO films even down to one unit cell at room temperature, which were stabilized in the PbTiO/SrTiO/PbTiO sandwich structures by in-plane tensile strain and interfacial coupling, as evidenced by large tetragonality (∼1.

Epitaxial Strain Enhanced Ferroelectric Polarization toward a Giant Tunneling Electroresistance.

A substantial ferroelectric polarization is the key for designing high-performance ferroelectric nonvolatile memories. As a promising candidate system, the BaTiO/LaSrMnO (BTO/LSMO) ferroelectric/ferromagnetic heterostructure has attracted a lot of attention thanks to the merits of high Curie temperature, large spin polarization, and low ferroelectric coercivity. Nevertheless, the BTO/LSMO heterostructure suffers from a moderate FE polarization, primarily due to the quick film-thickness-driven strain relaxation.

Pure Chiral Polar Vortex Phase in PbTiO/SrTiO Superlattices with Tunable Circular Dichroism.

Nontrivial polarization textures have been demonstrated in ferroelectric/dielectric superlattices, where the electrostatic, elastic, and different gradient energies compete in a delicate balance. When PbTiO/SrTiO superlattices are grown on DyScO, the coexistence of ferroelectric domains and vortex structure is observed for = 12-20 unit cells. Here, we report an approach to achieve single-phase vortex structures in superlattices by controlling the epitaxial strain using SrAlGaTaO substrates.

Absence of critical thickness for polar skyrmions with breaking the Kittel's law.

The period of polar domain (d) in ferroics was commonly believed to scale with corresponding film thicknesses (h), following the classical Kittel's law of d ∝ [Formula: see text]. Here, we have not only observed that this relationship fails in the case of polar skyrmions, where the period shrinks nearly to a constant value, or even experiences a slight increase, but also discovered that skyrmions have further persisted in [(PbTiO)/(SrTiO)] ultrathin superlattices. Both experimental and theoretical results indicate that the skyrmion periods (d) and PbTiO layer thicknesses in superlattice (h) obey the hyperbolic function of d = Ah + [Formula: see text] other than previous believed, simple square root law.

Atomic Insight into the Successive Antiferroelectric-Ferroelectric Phase Transition in Antiferroelectric Oxides.

Antiferroelectrics characterized by voltage-driven reversible transitions between antiparallel and parallel polarity are promising for cutting-edge electronic and electrical power applications. Wide-ranging explorations revealing the macroscopic performances and microstructural characteristics of typical antiferroelectric systems have been conducted. However, the underlying mechanism has not yet been fully unraveled, which depends largely on the atomistic processes.

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.

Antiferromagnetic switching driven by the collective dynamics of a coexisting spin glass.

The theory behind the electrical switching of antiferromagnets is premised on the existence of a well-defined broken symmetry state that can be rotated to encode information. A spin glass is, in many ways, the antithesis of this state, characterized by an ergodic landscape of nearly degenerate magnetic configurations, choosing to freeze into a distribution of these in a manner that is seemingly bereft of information. Here, we show that the coexistence of spin glass and antiferromagnetic order allows a novel mechanism to facilitate the switching of the antiferromagnet FeNbS, rooted in the electrically stimulated collective winding of the spin glass.

Defect-Enhanced Polarization Switching in the Improper Ferroelectric LuFeO.

Results of switching behavior of the improper ferroelectric LuFeO are presented. Using a model set of films prepared under controlled chemical and growth-rate conditions, it is shown that defects can reduce the quasi-static switching voltage by up to 40% in qualitative agreement with first-principles calculations. Switching studies show that the coercive field has a stronger frequency dispersion for the improper ferroelectrics compared to a proper ferroelectric such as PbTiO .

Large Scale Two-Dimensional Flux-Closure Domain Arrays in Oxide Multilayers and Their Controlled Growth.

Ferroelectric flux-closures are very promising in high-density storage and other nanoscale electronic devices. To make the data bits addressable, the nanoscale flux-closures are required to be periodic via a controlled growth. Although flux-closure quadrant arrays with 180° domain walls perpendicular to the interfaces (V-closure) have been observed in strained ferroelectric PbTiO films, the flux-closure quadrants therein are rather asymmetric.

BCL2/Ki-67 index predict survival in germinal center B-cell-like diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. BCL2 apoptosis regulator (BCL2) and marker of proliferation Ki-67 (Ki-67) are established prognostic markers, which have traditionally been assessed separately in DLBCL. However, no studies have evaluated the prognostic value of the combination of BCL2 and Ki-67 index.

Controlled Growth and Atomic-Scale Mapping of Charged Heterointerfaces in PbTiO/BiFeO Bilayers.

Functional oxide interfaces have received a great deal of attention owing to their intriguing physical properties induced by the interplay of lattice, orbital, charge, and spin degrees of freedom. Atomic-scale precision growth of the oxide interface opens new corridors to manipulate the correlated features in nanoelectronics devices. Here, we demonstrate that both head-to-head positively charged and tail-to-tail negatively charged BiFeO/PbTiO (BFO/PTO) heterointerfaces were successfully fabricated by designing the BFO/PTO film system deliberately.

Local Enhancement of Polarization at PbTiO/BiFeO Interfaces Mediated by Charge Transfer.

Ferroelectrics hold promise for sensors, transducers, and telecommunications. With the demand of electronic devices scaling down, they take the form of nanoscale films. However, the polarizations in ultrathin ferroelectric films are usually reduced dramatically due to the depolarization field caused by incomplete charge screening at interfaces, hampering the integrations of ferroelectrics into electric devices.

[Predictive value of tissue factor-associated platelet microparticles in thrombosis of patients with lymphoma].

This study was purposed to investigate the relationship between tissue factor associated platelet microparticles and thrombosis of patients with lymphoma by detecting the density of platelet microparticles and the tissue factor coagulative activity, and to evaluate the possibility of tissue factor coagulative activity for predication of thrombosis in lymphoma patients. This study was divided into 3 groups: A group including 50 healthy persons who did not take any drugs and had no hypercoagulation diseases; B group including 50 cases of lymphoma without thrombosis, and C group including 8 cases of lymphoma with thrombosis. The plasma was isolated from venous blood by centrifugation.

Matrix remodeling and endometriosis.

The physiological changes in endometriosis involving multiple steps of matrix remodeling include abnormal tissue growth, invasion, and adhesion formation. Endometriosis-associated abnormal matrix remodeling is affected by several molecular factors including proteolytic enzymes and their inhibitors, which mediate tissue turnover throughout the reproductive tract to maintain the integrity of the endometrium, and ovarian steroids, which normally regulate reconstruction and breakdown of endometrium in the menstrual cycle. In addition, various growth factors, such as platelet-derived growth factor, transform growth factor β, and epidermal growth factor, direct modulation of growth, activation, and chemotaxis which may facilitate endometrial cell adhesion onto the peritoneal mesothelium during the development of endometriosis.