The University of Nebraska-Lincoln physicist has found that, under certain conditions, the magnetic properties of a material can predict the relationship between its elasticity and temperature.His finding may point the way toward controlling the elasticity of certain materials by designing their magnetic properties or applying a magnetic field to them.In the meantime, knowing that magnetism alone can predict how elasticity will respond -- or not respond -- to changes in temperature might help engineers better select or design materials for specific purposes.Binek cited the 1986 disintegration of the Challenger space shuttle as a prominent example of elasticity's importance in engineering design.The hardening and failure of an elastic O-ring on Challenger's rocket booster -- a consequence of cold temperatures -- ultimately caused the shuttle to break apart, killing its seven crew members.The laws of thermodynamics describe the relationships among many factors -- temperature, entropy, volume, pressure -- that affect how heat gets converted into other forms of energy.
WASHINGTON, D.C., August 1, 2017 -- Flux-closure domain (FCD) structures are microscopic topological phenomena found in ferroelectric thin films that feature distinct electric polarization properties.However, a group of researchers in China has shown otherwise.Ferroelectric materials are typically developed and studied as thin films, sometimes as thin as only a few nanometers.As a result, researchers have begun discovering the abundant domain structures and unique physical properties that these ferroelectrics possess, such as skyrmion and FCD formation that could benefit next-generation electronic devices."The general thinking has been that oxide electrodes would destabilize flux-closure domains.However, our work has shown that this is no longer true when the top and bottom electrodes are symmetric, which physically makes sense," said Yinlian Zhu, professor at the Institute of Metal Research at the Chinese Academy of Sciences and a co-author of the paper.
Nagoya, Japan - Many next-generation electronic and electro-mechanical device technologies hinge on the development of ferroelectric materials.The unusual crystal structures of these materials have regions in their lattice, or domains, that behave like molecular switches.The alignment of a domain can be toggled by an electric field, which changes the position of atoms in the crystal and switches the polarization direction.These crystals are typically grown on supporting substrates that help to define and organize the behavior of domains.Control over the switching of domains when making crystals of ferroelectric materials is essential for any future applications.Now an international team by Nagoya University has developed a new way of controlling the domain structure of ferroelectric materials, which could accelerate development of future electronic and electro-mechanical devices.
Professor Martijn Kemerink of Linköping University has worked with colleagues in Spain and the Netherlands to develop the first material with conductivity properties that can be switched on and off using ferroelectric polarisation.The phenomenon can be used for small and flexible digital memories of the future, and for completely new types of solar cells.In an article published in the prestigious scientific journal Science Advances, the research group shows the phenomenon in action in three specially built molecules, and proposes a model for how it works."I originally had the idea many years ago, and then I just happened to meet Professor David González-Rodríguez, from the Universidad Autónoma de Madrid, who had constructed a molecule of exactly the type we were looking for," says Martijn Kemerink.The organic molecules that the researchers have built conduct electricity and contain dipoles.A dipole has one end with a positive charge and one with a negative charge, and changes its orientation (switches) depending on the voltage applied to it.
A team of researchers at the University Autonoma of Barcelona has created a new atomic force microscopy (AFM) technique that exploits the direct piezoelectric effect to take a measurement of the piezoelectric effect in ferroelectric materials.The technique, dubbed direct piezoelectric force microscopy, should enable a better understanding of piezoelectric and ferroelectric materials that form the basis of a number of today’s technologies, such as ultrasound generators for echography scanners, or, in the future, CMOS replacement switches.The piezoelectric effect, in which compressing or stretching a material produces a voltage, or where a voltage can cause a material to expand or contract, has been well characterized since the Curie brothers first measured it in 1880.However, ferroelectric materials—which can have their electric field polarization changed via an electric field—have only recently become better understood, in large part thanks to advances in AFM, in particular piezoresponse force microscopy (PFM).The PFM technique exploits what is termed the converse piezoelectric effect, which involves measuring the material deformation under an AC electric field that is being applied through the AFM tip that is in contact with the material’s surface.The Spanish researchers have taken this PFM technique, which is essentially an indirect measurement technique as it measures vibration by how much tip displacement occurs, and made it a direct measurement technique.
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties.Multiferroic materials show magnetically driven ferroelectricity.They are attracting increasing attention because of their fascinating properties such as magnetic (electric) field-controlled ferroelectric (ferromagnetic) properties and because they can be used in novel technological applications such as fast-writing, power-saving, and nondestructive data storage.However, because multiferroicity is typically observed at low temperatures, it is highly desirable to develop multiferroic materials that can be observed at room temperature.GaxFe2-xO3, or GFO for short, is a promising room-temperature multiferroic material because of its large magnetization.GFO thin films have already been successfully fabricated, and their polarization switching at room temperature has been demonstrated.
DURHAM, N.C. -- By ricocheting neutrons off the atoms of yttrium manganite (YMnO3) heated to 3,000 degrees Fahrenheit, researchers have discovered the atomic mechanisms that give the unusual material its rare electromagnetic properties.Such materials exist because their molecular structure consists of tiny magnetic patches that all point in the same direction.Ferroelectricity is a similar property, but more rare and difficult to conceptualize.This produces a naturally occurring permanent electric field, like a collection of microscopic balloons with a long-lasting charge of static electricity.This rare combination presents the interesting possibility of controlling the material's magnetic properties with electricity and vice versa.Harnessing this ability could let scientists create more efficient computers based on four digit-states rather than just today's 1s and 0s by flipping both electrical and magnetic states, as well as new types of sensors and energy converters.
But as engineers presented the latest research on ferroelectrics at the IEEE International Electron Devices Meeting (IEDM), in San Francisco in December, the mood in the room fluctuated between excitement and doubt.Still, the IEDM meeting made it clear that semiconductor companies are now paying attention.Researchers from GlobalFoundries presented data on the performance of ferroelectric-frosted transistors made using their 14- nanometer manufacturing technology.The magic of ferroelectrics is their potential to free engineers from the “Boltzmann tyranny,” named for Ludwig Boltzmann, who did foundational work in thermodynamics, says Aaron Franklin, an electrical engineer at Duke University, in North Carolina.As they get smaller, they do a worse job of shedding heat.Compared with those, the ferroelectric approach should be pretty straightforward.
Development of a theoretical basis for ultrahigh piezoelectricity in ferroelectric materials led to a new material with twice the piezo response of any existing commercial ferroelectric ceramics, according to an international team of researchers from Penn State, China and Australia.Piezoelectricity is the material property at the heart of medical ultrasound, sonar, active vibration control and many sensors and actuators.A piezoelectric material has the ability to mechanically deform when an electric voltage is applied or to generate electric charge when a mechanical force is applied.Adding small amounts of a carefully selected rare earth material, samarium, to a high-performance piezoelectric ceramic called lead magnesium niobate-lead titanate (PMN-PT) dramatically increases its piezo performance, the researchers report in Nature Materials this week."The majority of existing useful materials are discovered by trial-and-error experiments.But here we designed and synthesized a new piezoelectric ceramic guided by theory and simulations."
Ferroelectric crystals display a macroscopic electric polarization, a superposition of many dipoles at the atomic scale which originate from spatially separated electrons and atomic nuclei.The macroscopic polarization is expected to change when the atoms are set in motion but the connection between polarization and atomic motions has remained unknown.A time-resolved x-ray experiment now elucidates that tiny atomic vibrations shift negative charges over a 1000 times larger distance between atoms and switch the macroscopic polarization on a time scale of a millionth of a millionth of a second.This calls for understanding the connection between atomic structure and macroscopic electric properties, including the physical mechanisms governing the fastest possible dynamics of macroscopic electric polarizations.Researchers from the Max Born Institute in Berlin have now demonstrated how atomic vibrations modulate the macroscopic electric polarization of the prototype ferroelectric ammonium sulphate [Fig.1] on a time scale of a few picoseconds (1 picosecond (ps) = 1 millionth of a millionth of a second).
Lobachevsky University scientists have obtained the main representatives of the family of Aurivillius phases: Bi2MoO6, Bi2WO6, Bi3NbTiO9, Bi4Ti3O12 and CaBi4Ti4O15.The Aurivillius phases have long remained the main candidate materials for producing nonvolatile memory chips.Currently, existing random access memory types are volatile, i.e.The desire to equip computers with non-volatile memory has long been evident.Ferroelectrics are substances that have spontaneous electric polarization in the absence of an external electric field in a certain temperature range.The scientific and practical interest in Aurivillius phases is based on the transition from the ferroelectric state to the paraelectric phase, which is accompanied by the disappearance of spontaneous polarization.
In 1965, a renowned Princeton University physicist theorized that ferroelectric metals could conduct electricity despite not existing in nature.For decades, scientists thought it would be impossible to prove the theory by Philip W. Anderson, who shared the 1977 Nobel Prize in physics.It was like trying to blend fire and water, but a Rutgers-led international team of scientists has verified the theory and their findings are published online in Nature Communications."It's exciting," said Jak Chakhalian, a team leader of the study and Professor Claud Lovelace Endowed Chair in Experimental Physics at Rutgers University-New Brunswick."We created a new class of two-dimensional artificial materials with ferroelectric-like properties at room temperature that don't exist in nature yet can conduct electricity.None of their materials conducts electricity and the Rutgers-led findings potentially could spawn a new generation of devices and applications, Chakhalian said.
Because of this unique property, ferroelectrics can be found in anything from ultrasound machines and diesel fuel injectors to computer memory.Ferroelectric materials are behind some of the most advanced technology available today.New findings published in Applied Physics Letters, from AIP Publishing, help to shine light on these materials and indicate potential for new optoelectronic and storage applications.The group investigated the material's ferroelectric, magnetoelectric and optical properties.They were able to demonstrate ferroelectricity in Ca3Mn2O7 as well as coupling between its magnetism and ferroelectricity, a key property that has potential to allow for faster and more efficient bit operations in computers.Like batteries, for instance, ferroelectrics have positively and negatively charged poles.
OAK RIDGE, Tenn., Sept. 25, 2018--A unique combination of imaging tools and atomic-level simulations has allowed a team led by the Department of Energy's Oak Ridge National Laboratory to solve a longstanding debate about the properties of a promising material that can harvest energy from light.This finding was contrary to previous assumptions that the material is ferroelectric, meaning it can form domains of polarized electric charge to minimize electric energy."We found that people were misguided by the mechanical signal in standard electromechanical measurements, resulting in the misinterpretation of ferroelectricity," said Yongtao Liu of ORNL, whose contribution to the study became a focus of his PhD thesis at the University of Tennessee, Knoxville (UTK).The findings, reported in Nature Materials, revealed that differential strains cause ionized molecules to migrate and segregate within regions of the film, resulting in local chemistry that may affect the transport of electric charge.The understanding that this unique suite of imaging tools enables allows researchers to better correlate structure and function and fine-tune energy-harvesting films for improved performance.To relieve the strain, tiny ferroelastic domains formed.
Only now in 2018 have researchers successfully demonstrated that hypothetical 'particles' that were proposed by Franz Preisach in 1935 actually exist.In an article published in Nature Communications, scientists from the universities in Linköping and Eindhoven show why ferroelectric materials act as they do.Iron, cobalt and nickel are examples of common ferromagnetic materials.In absence of an applied magnetic (for a ferromagnet) or electric (for a ferroelectric) field, the orientation of the dipoles is random.For a piece of ideal ferroelectric material, the whole piece switches its polarization when the critical field is reached and it does so with a well-defined speed.Understanding this non-ideality is key to the application in memories.
As a part of JST PRESTO program, Associate professor Masaharu Kobayashi, Institute of industrial Science, The University of Tokyo, has experimentally clarified the operation mechanism of low voltage operation of a transistor with ferroelectric-HfO2 gate insulator.In addition, he has theoretically elucidated scalability of ferroelectric tunnel junction (FTJ) memory with ferroelectric-HfO2 down to 20nm diameter.Negative capacitance FET (NCFET) with ferroelectric-HfO2 gate insulator is attracting interests as a steep subthreshold slope transistor for ultralow voltage operation, which can break the physical limit of 60mV/dec in the conventional MOSFET.However, its operation mechanism has not been fully clarified yet in terms of polarization switching dynamics.FTJ memory with ferroelectric-HfO2 is a promising high-capacity nonvolatile memory.However, its scalability considering resistance ratio between read current for access speed, resistance ratio between on-state and off-state for sensing margin, depolarization field for retention characteristics has not been fully elucidated yet.
A team of researchers from Lehigh University, Oak Ridge National Laboratory, Lebanon Valley College and Corning Inc. has demonstrated, for the first time, that crystals manufactured by lasers within a glass matrix maintain full ferroelectric functionality."This includes the ability to uniformly orient and reverse orient the ferroelectric domains with an electric field?despite the fact that the crystal is strongly confined by the surrounding glass," says Volkmar Dierolf, Chair of Lehigh University's Department of Physics and one of the scientists who worked on the experiments that resulted in these findings.Dierolf, who holds a joint appointment with Lehigh's Department of Materials Science and Engineering part of the P.C.Rossin College of Engineering and Applied Science, is co-Principal Investigator on a National Science Foundation (NSF)-funded project, Crystal in Glass, along with Principal Investigator Himanshu Jain, Diamond Distinguished Chair of Lehigh's Department of Materials Science and Engineering.The group has become a world leader in producing single crystals in glass by localized laser irradiation.Read more about their work: "Crossing a critical threshold" and "Lehigh scientists fabricate a new class of crystalline solid."
Some perovskite oxides, for example, have shown a wide spectrum of technologically relevant functional properties such as ferroelectricity and magnetism that can be tuned via strain.SrMnO3 (SMO) is a particularly interesting example for examining the functionality resulting from a complex interplay of strain, magnetic order, polar distortions, and oxygen vacancies that are ubiquitous defects in these materials.In particular, theory has predicted SMO thin films to turn from antiferromagnetic to ferromagnetic with increasing oxygen deficiency, which is supported by recent experimental studies.These previous predictions were however based on density functional theory (DFT) calculations that incorporated a correction U based on the electronic and magnetic properties of stoichiometric manganites.While the inclusion of U--meant to correct self-interaction of electrons in complex oxides--is necessary in such materials, the specific choice of U based on stoichiometric material properties could lead to potential shortcomings in the description of defective SMO--manganese ions around the defect have a different coordination environment.Depending on the defect charge state, an added issue is related to the description of multiple oxidation states present in defective SMO.
As a part of JST PRESTO program, Associate professor Masaharu Kobayashi, Institute of Industrial Science, the University of Tokyo, has developed a ferroelectric FET (FeFET) with ferroelectric-HfO2 and ultrathin IGZO channel.Nearly ideal subthreshold swing (SS) and mobility higher than poly-silicon channel have been demonstrated.FeFET is a promising memory device because of its low-power, high-speed and high-capacity.For even higher memory capacity, 3D vertical stack structure has been proposed as shown in Fig.This results in voltage loss and charge trapping which prevents low voltage operation and degrades reliability, respectively as shown in Fig.To solve these problems, in this study, we proposed a ferroelectric-HfO2 based FeFET with ultrathin IGZO channel.
In a paper released today in Science Advances, UNSW researchers describe the first observation of a native ferroelectric metal."We found coexistence of native metallicity and ferroelectricity in bulk crystalline tungsten ditelluride (WTe2) at room temperature," explains study author Dr Pankaj Sharma."We demonstrated that the ferroelectric state is switchable under an external electrical bias and explain the mechanism for 'metallic ferroelectricity' in WTe2 through a systematic study of the crystal structure, electronic transport measurements and theoretical considerations."A ferromagnetic material displays permanent magnetism, and in layperson's terms, is simply, a 'magnet' with north and south pole.This spontaneous electric dipole moment can be repeatedly transitioned between two or more equivalent states or directions upon application of an external electric field - a property utilised in numerous ferroelectric technologies, for example nano-electronic computer memory, RFID cards, medical ultrasound transducers, infrared cameras, submarine sonar, vibration and pressure sensors, and precision actuators.Conventionally, ferroelectricity has been observed in materials that are insulating or semiconducting rather than metallic, because conduction electrons in metals screen-out the static internal fields arising from the dipole moment.
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