Researchers at the Institute of Metal Research at the Chinese Academy of Sciences have discovered large-scale periodic arrays of flux-encapsulated domain structures and alternate arrangements of clockwise and counterclockwise closed structures in ferroelectric materials. On April 16th, the Science Weekly of the United States took the lead through Science Express to publish the research results online and formally publish it in Report form in a few weeks.
This work was carried out by Zhang Zhidong, a researcher of the material interface electron microscopy team and the magnetic and magnetic materials research department of the Shenyang Institute of Materials Science (Joint) National Solid State Research Institute of Materials Science and Technology, Ma Xiuliang, Zhu Yinlian, and Tang Yunlong. The cooperation between Ukrainian and U.S. scientists was completed.
Ferroelectric materials and ferromagnetic materials have strong similarities, such as similar electrical (magnetic) hysteresis loops, polarization order parameters and domain structure configuration and so on. Compared with the more mature research and application in the field of ferromagnetics, the basic and applied research of ferroelectric materials lags behind, reflecting the difference in the physical nature of the two. Since 1986, physicists have predicted that full-closed fluxes may occur in ferroelectric materials under certain conditions, and theoretically the structure can bring ultra-high-density information storage functions.
Although flux fully-closed structures have been widely recognized in ferromagnetic materials, after nearly 30 years of exploration, they have not been confirmed in ferroelectric materials. The main difficulty is that the flux completely closed structure in the ferroelectric material will inevitably lead to a huge lattice strain. How to break through the mutual restraint of ferroelectric polarization and lattice strain, achieve effective control of polarization reversal and lattice strain, and obtain structural units that are expected to be used for ultra-high-density information storage are a major foundation for ferroelectric materials today. Sexual science problems.
Shenyang Institute of Materials Science (National) Joint Research Center for Solid Atomic Image Interfacial Structures at the National (Joint) Laboratory of Materials Science has long been dedicated to the study of electron microscopy of basic materials science issues. After many years of academic accumulation and cooperation with related scientists at home and abroad, the above major Breakthrough in scientific problems.
They implemented a series of ultra-thin PbTiO3 ferroelectric thin films on a germanate substrate through reverse-thinking design and strain control. Using aberration-corrected electron microscopy with atomic-scale resolution, they not only found that the flux was completely closed. Structures and their novel atomic configuration maps, and observations of large-scale periodic arrays consisting of alternate arrangements of clockwise and counterclockwise closed structures. On this basis, they revealed the formation law of periodic closed structures and found that the linear relationship between the periodic size of the periodic array formed by the flux closed structure and the thickness of the thin film is within a certain range of film thickness. The large strain gradient at the core of the closed structure (109/m) and the large long-range elastic strain gradient (106/m) in the closed structure are deduced; the current highest volume at the core of the closed structure is calculated in the framework of Landau-Ginsburg-Devonshire theory. Grade bending constant (10-10C-1m3).
This work changed the previous research idea of ​​searching for flux-closed ferroelectric domain structures, further improved the importance and effectiveness of the domain structure and physical properties of ferroelectric materials modulated by mismatch strain, and solved the domain wall configuration in ferroelectric fields. The major fundamental scientific issues that have been pending for decades have added new substantive content to the structural characteristics of ferromagnetic materials. The discovery of full-closed flux structure and large bending effect in ferroelectric materials will push the design and R&D of ferroelectric thin film devices to a new level, providing a new way to explore high-density information storage based on ferroelectric materials. . At the same time, this work has confirmed that a huge elastic strain gradient can be preserved in the form of a multilayer film, achieving continuous control of the relevant physical properties, and providing new ideas for the design of new gradient functional materials.
Wang Yujia, a researcher in the Department of Solid Atoms, and Ph.D. students Wang Wenyuan and Xu Yaobin also participated in this work.
US "Science" weekly selects a few articles from the recently accepted manuscripts and publishes the author's final revised manuscripts through the Science Express platform. This will provide readers with major scientific advances or policy views, etc. at the first time. Latest News. These work will be officially published in the "Science" weekly in both online and paper format 4 to 6 weeks later, and are usually the most important articles recommended by editors.
The study was funded by the National Natural Science Foundation and the "973" Program of the Ministry of Science and Technology.
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