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Determinarea structurilor produselor farmaceutice nanocristaline prin difracție electronică

Posted: Feb 26, 2016

Determining the structures of nanocrystalline pharmaceuticals by electron diffraction

(Nanowerk News) Reliable information about the structure of pharmaceutical compounds is important for patient safety, for the development of related drugs and for patenting purposes. However, working out the structures of pharmaceuticals can be tough.
90° cut-off schematic of the camera as designed for the CM200
90° cut-off schematic of the camera as designed for the CM200 (Technische Universiteit Delft, The Netherlands).The individual molecules can pack together in the solid in different ways to form different polymorphs, and pertinent properties such as stability, bioavailability or how fast they dissolve in the stomach can vary from one polymorph to another. Single crystals (as used in standard X-ray diffraction experiments) therefore might not be representative of the bulk sample, or indeed might not even be available.

Moreover, the compounds themselves can be damaged by the high energy of the X-radiation used. As electrons are less damaging than X-rays by several orders of magnitude, using electron diffraction should be an attractive alternative, particularly when only nanometre-sized crystals are available. Cooling the sample to liquid-nitrogen temperatures (‘cryo-cooling’) can also help to minimize radiation damage, but the compound might change structure on cooling, so the structure that is obtained is not actually that of the material as taken by the patient at room temperature.

A group of scientists from a number of European countries have tackled all aspects of these problems by using low-dose electron diffraction, rotating the sample so that individual nanocrystals are not in the electron beam long enough to be damaged and collecting the diffraction data using a new type of detector developed by CERN („Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector”).
This new detector combines a high dynamic range with a very high signal-to-noise ratio and sensitivity to single electrons. Radiation damage was reduced so much that cooling the sample was not found to be necessary, allowing the team to study the anticonvulsant drug carbamazepine and nicotinic acid (vitamin B3) at room temperature. The data they collected were high enough quality that they could solve the structures of the two compounds using direct methods and software developed for X-ray crystallography.
Based on their experience with these case studies, the authors are planning to improve the design of their experimental setup further, and will also be developing programs specifically designed for handling electron-diffraction data.
Source: International Union of Crystallography

Read more: Determining the structures of nanocrystalline pharmaceuticals by electron diffraction

O metastră acustică super-subțire pentru o absorbție perfectă a sunetului(A super-thin acoustic metasurface for perfect sound absorption)

Aplicațiile ulterioare ale unei astfel de metafore se pot referi la realizarea amplitudinii și a profilului de fază reglabil pentru ingineria acustică, care ar permite manipularea unei traiectorii de propagare a undelor acustice pentru aplicații speciale

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Atomii de cupru au fost făcuți pentru a leza la lungimi de undă ultra-scurte cu raze X (Copper atoms made to lase at ultrashort x-ray wavelengths )

laserele atomice generează raze X cu distribuții mult mai clare ale lungimii de undă și o coerență temporală mai mare pe durata impulsului. În consecință, laserul atomic cu carcasă atomică are un potențial interesant pentru o astfel de cercetare. „Ne așteptăm ca această tehnologie poate fi aplicată, de exemplu, pentru a explora interferență cuantică pe un zeptosecond [10 -21 mărfuri de calitatea a două] la scară“

Posted: Feb 05, 2016

Copper atoms made to lase at ultrashort x-ray wavelengths

(Nanowerk News) Using RIKEN’s powerful SACLA x-ray free-electron laser (XFEL) facility, researchers have developed the world’s first atomic x-ray laser capable of generating high-energy (‘hard’) x-rays with an ultrashort wavelength of just 1.5 ångströms (or 0.15 nanometers)—almost ten times shorter than the wavelengths of x-rays produced by earlier atomic lasers („Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser”).
Photograph of the experimental setup used to achieve a copper atomic x-ray laser
Photograph of the experimental setup used to achieve a copper atomic x-ray laser. The copper foil target is mounted in the sample chamber (left) and is bombarded with an x-ray beam (from right) generated by the SACLA x-ray free-electron laser. (Image: Makina Yabashi, RIKEN SPring-8 Center)
Almost half a century ago, scientists theoretically predicted that copper atoms could be made to lase in the x-ray region by exciting them with x-rays of a suitable wavelength. The incident x-rays eject electrons from inner electron shells, resulting in a cascade of electron energy drops that produce light at a very specific wavelength of 1.5 ångströms—a length similar to the diameter of a copper atom. The emitted photons are then amplified by interacting with other excited copper ions, resulting in a process known as amplified spontaneous emission (ASE). Until now, this kind of x-ray amplification had been impossible to achieve in the lab due to the inconceivably high excitation intensities it demands.
Now, Hitoki Yoneda of the University of Electro-Communications and RIKEN SPring-8 Center and Makina Yabashi of RIKEN SPring-8 Center with their co-workers have succeeded in stimulating ASE of hard x-rays and used it to produce laser pulses with a wavelength of 1.5 ångströms. They realized this by shining very short pulses of intense x-rays from SACLA onto a copper foil (Fig. 1). ASE was further enhanced by combining the excitation ‘pump’ pulse with a ‘seed’ pulse from the same XFEL excitation source operating in two-color mode—a unique functionality of SACLA.
“We needed an extremely intense x-ray beam to create the highly excited states of copper atoms,” explains Yabashi. “The SACLA x-ray source has the highest intensity in the world, which we combined with state-of-the-art x-ray optics technology to focus the XFEL beam to a spot just 100 nanometers in diameter.” With this approach, the team achieved an unprecedented power density of about 1019 watts per square centimeter.
Although x-ray free-electron lasers are capable of producing hard x-rays at ångström wavelengths—SACLA itself supplies a 1.4-ångström x-ray pulse to stimulate ASE from the copper foil—they produce ‘fuzzy’ beams at such short wavelengths. This fuzziness poses problems for probing phenomena at very short time scales or spatial scales approaching the laser wavelength.
In contrast, atomic lasers generate x-rays with much sharper wavelength distributions and higher temporal coherence over the pulse duration. Consequently, the atomic inner-shell laser has exciting potential for such research. “We expect this technology may be applied, for example, to explore quantum interference on a zeptosecond [10-21 second] scale,” notes Yabashi.
Source: RIKEN

Read more: Copper atoms made to lase at ultrashort x-ray wavelengths

Frigiderul cuantic

Înlătură termen: particulele cu cea mai mare energie sunt îndepărtate din gaz. Ceilalți interacționează particulele cu cea mai mare energie sunt îndepărtate din gaz. Ceilalți interacționeazăÎnlătură termen: răcirea gazelor reci: cu ajutorul câmpurilor electromagnetice răcirea gazelor reci: cu ajutorul câmpurilor electromagneticeÎnlătură termen: redistribuie energia și gazul se relaxează din nou la o distribuție tipică a energiei – dar la o temperatură ușor mai scăzută decât înainte. redistribuie energia și gazul se relaxează din nou la o distribuție tipică a energiei – dar la o temperatură ușor mai scăzută decât înainte.

Posted: Feb 01, 2016

The quantum fridge

(Nanowerk News) When cold milk is poured into a hot cup of tea, a temperature equilibrium is reached very quickly. The milk droplets and the tea particles interact, and after a few moments they all have the same average energy. This process is called thermalization. It plays a crucial role in cooling down gases to ultra-low temperatures. But surprisingly, even gases for which this effect is suppressed can be cooled. Scientists at TU Wien (Vienna) took a closer look at this phenomenon and found a special quantum-mechanical kind of cooling at work (Physical Review Letters, „Cooling of a One-Dimensional Bose Gas”).
Kicking Out Hot Particles
“The particles that make up a liquid or a gas have different energies”, says Professor Jörg Schmiedmayer (TU Wien). The distribution of these energies depends on the temperature. The hotter the gas, the higher the number of particles with high energies. Therefore, a simple trick can be used to cool down cold gases: with the help of electromagnetic fields, the particles with the highest energy are removed from the gas. The remaining ones interact, redistribute the energy, and the gas relaxes again to a typical energy distribution—but at a slightly lower temperature than before.
“It is a bit like blowing on your tea in order to cool it”, says Bernhard Rauer, who led the experiments in Schmiedmayer’s research group. “The particles with the highest energy manage to leave the liquid and are blown away. The remaining tea quickly reaches an equilibrium state at a slightly lower temperature.”
Bernhard Rauer in the lab at TU Wien
Bernhard Rauer in the lab at TU Wien.
However, there are cases, in which reaching such a thermal equilibrium is not possible. A Newton’s cradle for example is a device that has several spheres hanging from strings, arranged in a straight line. When one of the spheres is set in motion and hits the others, the last sphere in line is kicked away, while the others do not move. “In this case, the spheres can only exchange energies between each other. There will never be a thermal distribution of many different energies”, says Bernhard Rauer.
Rauer studied a similar system: a one dimensional gas of atoms, kept in a straight line by an electromagnetic trap. The atoms can just exchange their energies, just like the spheres in Newton’s cradle. Therefore, one would expect the cooling mechanism of removing the most energetic particles to fail in this case. When the fastest particles are gone, no other particles in the gas will ever have the same speed again. According to this simple model, an energy that is missing will be gone forever.
Astonishingly, this is not true for the one-dimensional gas. It can be cooled down by continuously removing particles—to much lower energies than one would expect, according, to the simplified picture of fast and slow particles.
It’s a Wave!
The reason for this effect is that the particles can only be understood quantum mechanically. “We should not think of individual particles colliding like the spheres in Newton’s cradle. Instead, we have to consider collective excitations, which are distributed across many particles – like a water wave, which is carried by many water molecules at the same time”, says Jörg Schmiedmayer. These quantum waves store the energy of the system, and the more particles that are removed from the gas, the less intense these waves become. This is a quantum mechanical cooling mechanism which should be impossible according to simple classical laws of nature.
“For us it is crucial that the gas behaves more and more quantum mechanically at low temperatures”, says Jörg Schmiedmayer. “That is exciting, because that is precisely what we are interested in: often quantum physics is studied in simple systems, consisting only of a few particles, such as an atom with a few electrons. We have a system which undeniably exhibits quantum behaviour, and it is made of thousands of atoms.”
Source: Vienna University of Technology

Read more: The quantum fridge

O cale pentru valurile de centrifugare

Spin este termenul pe care oamenii de știință îl folosesc pentru a descrie unghiul angular al electronilor care se rotesc în jurul axei proprii. Aceasta face particulele electrice să se comporte ca niște magneți extrem de mici. Acesta este motivul pentru care se aliniază într-o manieră paralelă în materiale feromagnetice. „Dacă cineva conduce o rotație într-o direcție diferită, acest lucru va avea un impact și asupra rotirilor învecinate”, explică Schultheiß. „Aceasta creează un val de spin care călătorește prin corpul solid. Poate fi folosit pentru a transporta și procesa informații, la fel ca purtătorii de încărcături care curg”. Cu toate acestea, electronii înșiși nu se mișcă în acest caz. „Ei nu se ciocnesc cu nimic și, prin urmare, nu generează aproape nici unul

Posted: Feb 01, 2016

A highway for spin waves

(Nanowerk News) The success story of information processing by way of moving electrons is slowly coming to an end. The trend towards more and more compact chips constitutes a major challenge for manufacturers, since the increasing miniaturization creates partly unsolvable physical problems. This is why magnetic spin waves could be the future: they are faster than electronic charge carriers and use less power. Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and TU Dresden have developed a method for controlling the propagation of these information carriers at the nanolevel in a targeted and simple way; so far, this required a lot of power. They have thus created a basis for nanocircuits that use spin waves (Nature Nanotechnology,„Magnetic domain walls as reconfigurable spin-wave nanochannels”).
Domain Wall
The spin wave remains trapped in the domain wall, which is formed in the middle between the differently oriented magnetizations. Researchers at the HZDR could thus control its propagation purposefully. (Image: HZDR / H. Schultheiß)
„Our current information processing is based on electrons,” explains Dr. Helmut Schultheiß from the HZDR’s Institute of Ion Beam Physics and Materials Research. „These charged particles flow through the wires, creating electric currents. Yet in the process they collide with atoms and lose energy, which escapes into the crystal lattice in the form of heat. This means that chips get all the warmer, the closer the elements on them are grouped together. Eventually they fail, because the heat cannot be conveyed anymore.” This is why Schultheiß, head of an Emmy Noether Junior Research Group, pursues a different approach: information transport via spin waves, also known as magnons.
The magnetic moment of electrons
Spin is the term scientists use to describe the angular momentum of electrons revolving around their own axis. It makes the electric particles behave like extremely small magnets. This is why they align in a parallel manner in ferromagnetic materials. „If one guides a spin in a different direction, this will have an impact also on the neighboring spins,” Schultheiß explains. „This creates a spin wave that travels through the solid body. It can be used to transport and process information just like flowing charge carriers.” However, the electrons themselves do not move in this case. „They do not collide with anything and therefore generate hardly any heat.”
Yet in order to prevail in the race for future information processing methods, systems are needed that allow for controlling the propagation of spin waves at the nanolevel. „So far, approaches to a solution were based either on geometrically predefined conductor paths or on the permanent use of external magnetic fields,” says Schultheiß, explaining the current state of research. „In the case of the first solution, the propagation path cannot be changed; however this is necessary for the development of flexible circuits. The second method solves that problem, yet at the price of an enormous increase in power consumption.”
Controlled propagation path
The scientists have successfully developed a new procedure for the targeted steering of spin waves by utilizing basic magnetic characteristics: remanence, that is, the residual magnetism that a solid body retains after the removal of a magnetic field, and the formation of so-called domain walls. „This term denotes the area in solid bodies where differently aligned magnetic domains meet,” Schultheiß explains.
The HZDR researchers created such a domain wall within a nickel-iron alloy nanostructure in an experiment. They then triggered a spin wave using microwaves. As their tests have shown, the spin waves of a certain frequency got stuck in the domain wall, because the different magnetic domains act as barriers. „In a sense, one could say that we created a road with a crash barrier along which the spin waves travel in a controlled manner,” Schultheiß cheerfully describes the result.
However, the Dresden physicists were able to celebrate yet another success. They manipulated the course of the domain wall by way of small external magnetic fields of far below one millitesla, about one hundred times weaker than a commercial horseshoe magnet. In doing so, they likewise manipulated the propagation of the spin waves. „This could be the basis for a design of reconfigurable nanocircuits that uses magnons,” Schultheiß says, sizing up the options. Even so, the researcher thinks that several years are likely to pass before application. „We are still in the basic research phase. However, our results reveal that we are onto a good thing.”
Source: Helmholtz-Zentrum Dresden-Rossendorf

Read more: A highway for spin waves

Picăturile lichide arată capacitatea de a răci suprafețe extrem de fierbinți(A heat-seeking slingshot: Liquid droplets show ability to cool extremely hot surfaces)

Aceasta împiedică picăturile lichidului să facă contact fizic cu suprafața, determinându-le, în schimb, să se hrănească deasupra suprafeței. Și cauzează picăturile să se fiarbă mai încet decât ar face-o pe o suprafață cu o temperatură mai scăzută care este încă deasupra punctului de fierbere al lichidului.

Posted: Feb 01, 2016

A heat-seeking slingshot: Liquid droplets show ability to cool extremely hot surfaces

(Nanowerk News) Turn on a skillet and let it heat up until it is well above the boiling point of water. Then sprinkle a teaspoon of water on the skillet and watch. Water droplets will bounce up, form spheres and scurry across the surface.
What you have just observed is an example of the Leidenfrost effect, named for Johann Gottlob Leidenfrost, an 18th-century German physician and scientist. The phenomenon occurs when a liquid, upon approaching an object that is much hotter than the liquid’s boiling point, produces a vapor which insulates the liquid from the surface of the object.
Researchers in Hong Kong and at Lehigh University recently demonstrated that it is possible to exploit the Leidenfrost effect to control the direction and destination of liquid droplets on a surface and thus to cool it more efficiently. They achieved this by lithographically patterning a surface with microscale features that convert excess surface tension into a kinetic energy that propels droplets to „hot spots” on the surface.
The discovery, say Zuankai Wang of the City University of Hong Kong and Manoj Chaudhury of Lehigh, has the potential to improve technologies that involve microfluidics, heat transfer, heat exchange, micro-heat exchange, water management and thermal management.
„Many applications, such as power plant reactors, require the management and control of the movement of water droplets at very high temperatures,” says Wang, an associate professor of mechanical and biomedical engineering at City University. „Typically, the cooling of extremely hot surfaces has been accomplished with spray cooling. You spray a lot of water droplets onto a surface and as they boil, they take away the heat.
„At a high temperature, however, this doesn’t work because the Leidenfrost effect prevents the droplets from making sufficient contact with the surface to cool it. Thus it takes too long to cool a surface by boiling off water.”
Wang, Chaudhury and their colleagues reported their results today (Feb. 1) in Nature Physics(„Directional transport of high-temperature Janus droplets mediated by structural topography”). The article’s lead author is Jing Li, a Ph.D. candidate in the department of mechanical and biomedical engineering at City University.
Contrasting topographies
Scientists in the last 20 years have learned to control the movement of liquid droplets on a solid surface by breaking the wetting symmetry that results from the impact of a droplet on a surface. They have accomplished this by harnessing gradients of surface energy and by utilizing light, temperature, electric force and mechanical vibration.
Chaudhury, the Franklin J. Howes Jr. Distinguished Professor of Chemical and Biomolecular Engineering at Lehigh, for example, has published articles with his students in Science and Langmuir describing their successful efforts to direct the movement of water droplets on surfaces.
But scientists have not yet achieved this control on surfaces heated to Leidenfrost temperatures and above, or on surfaces with extremely hot local spots.
Two years ago, Wang came up with the idea of creating topographical contrasts on a silicon wafer by etching the wafer surface with micropillars and arranging the pillars in zones that vary according to the density of the pillars and the contact angle of the pillars with the surface.
„The Leidenfrost Effect has been extensively studied for drag reduction, while the presence of the undesired vapor layer also prevents efficient heat transfer,” says Wang. „Thus, we came up with the idea of creating an asymmetric surface to control droplet motion at high temperatures.”
In their Nature Physics article, the researchers reported that their experiments, which were conducted in Hong Kong, showed that „judicious control of the structural topography and operating temperature range of the solid substrate” served to break the wetting symmetry of droplets.
The group also reported a „new physical phenomenon in which two concurrent wetting states–Leidenfrost and contact-boiling–can be designed in a single droplet [heated] above its boiling point.”
The droplet, the researchers wrote in Nature Physics, „exhibits a contrasting (or Janus) thermal state with a lower contact angle in the boiling region, but a higher angle in the Leidenfrost region.” This contrast generates „a gradient of curvature, and thus a gradient of Laplace pressure.”
„As the [droplet’s] viscous dissipation is minimal,” the researchers wrote, „the resulting excess surface energy of the droplet is converted to kinetic energy, naturally causing it to dislodge from the surface and take flight into the air. The droplet eventually gets deposited in the contact-boiling region.”
A similar phenomenon in nature
The researchers liken this phenomenon to the action of a slingshot and note that something similar occurs with a filamentous mushroom called Basidiomycota. Each spore of the fungus is part hydrophobic, with a shape like a thin film, and part hydrophilic, with a shape like a sphere. When the two regions make contact, they coalesce, and the tension between hydrophobic and hydrophilic regions creates a force that carries the entire spore into the air.
„This is a chemical effect that nature produces,” says Shuhuai Yao, an associate professor of mechanical and aerospace engineering at the Hong Kong University of Science and Technology. „At the point of coalescence, there is an asymmetry but the desire for symmetry causes a transitory state and generates a force that propels the spore.”
The contrasting topographies of the micropillars on Wang’s silicon wafer create a similar phenomenon. At a high temperature, as one part of the droplet is boiling and one is non-boiling, an asymmetry is created. But as with the Basidiomycota, the natural tendency toward symmetry creates the slingshot effect that propels the droplet.
There is, however, a critical difference between the two phenomena, the researchers say. While nature makes no effort to guide a spore but instead merely to release it, a droplet on a bio-inspired surface can be targeted to a specific place and made to land on a hot spot and boil off.
Source: Lehigh University

Read more: A heat-seeking slingshot: Liquid droplets show ability to cool extremely hot surfaces

Polar vortex observate în feroelectrice

Materialele feroase prezintă proprietăți electrice sau magnetice unice – sau ambele în cazul multiferroizelor. De exemplu, câmpul electric al unui material feroelectric poate fi polarizat în favoarea unei încărcări pozitive sau negative cu aplicarea unui câmp electric extern. Într-un material feromagnetic, aplicarea unui câmp magnetic extern aliniază rotația particulelor încărcate, rezultând materialul devenind un magnet permanent. În ultimii ani, sa descoperit că aplicarea unui câmp magnetic extern poate produce, de asemenea, cicloane cu dimensiuni atomice de cercuri, care acționează ca particule de baryon și pot fi deplasate coerent pe distanțe macroscopice. Aceste proprietăți fac Skyrmions candidați excelenți pentru aplicații spintronice.

Posted: Jan 29, 2016

Polar vortices observed in ferroelectric

(Nanowerk News) The observation in a ferroelectric material of „polar vortices” that appear to be the electrical cousins of magnetic skyrmions holds intriguing possibilities for advanced electronic devices. These polar vortices, which were theoretically predicted more than a decade ago, could also „rewrite our basic understanding of ferroelectrics” according to the researchers who observed them.
A team of scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have recorded the first ever observations of rotating topologies of electrical polarization that are similar to the discrete swirls of magnetism known as „skyrmions.” If these smoothly rotating vortex/anti-vortex topologies prove to be electrical skyrmions, they could find potential applications in ultracompact data storage and processing, and could also lead to the production of new states of matter and associated phenomena in ferroic materials.
polar vortices in a ferroelectic material
The first ever observations of polar vortices in a ferroelectic material could find potential applications in ultracompact data storage and processing and the production of new states of matter.
„It has long been thought that rotating topological structures are confined to magnetic systems and aren’t possible in ferroelectric materials, but through the creation of artificial superlattices, we have controlled the various energies of a ferrolectric material to promote competition that lead to such new states of matter and polarization arrangements,” says Ramamoorthy Ramesh, Berkeley Lab’s Associate Laboratory Director for Energy Technologies and the co-principal investigator for this study. He also holds UC Berkeley’s Purnendu Chatterjee Endowed Chair in Energy Technologies.
„Ferroelectric materials such as the materials used in this work have produced a number of exciting emergent properties over the years, but these smoothly-rotating polar vortex structures really are different,” says Lane Martin, a faculty scientist with Berkeley Lab’s Materials Sciences Division and Associate Professor in UC Berkeley’s Department of Materials Science and Engineering, who is this study’s co-principal investigator. „I think if you surveyed the community many would shake their heads in disbelief at such structures, but it turns out there really is a tendency for vortex states to form in nature even in these polar systems. And, when one looks more broadly, vortex structures can occur across huge length scales – from galaxies and weather systems all the way down to 10s of atoms as in our case.”
Ramesh and Martin are the corresponding authors of a Nature paper describing this study in detail („Observation of polar vortices in oxide superlattices”).
Ferroic materials display unique electrical or magnetic properties – or both in the case of multiferroics. For example, the electrical field of a ferroelectric material can be polarized in favor of either a positive or negative charge with the application of an external electrical field. In a ferromagnetic material, the application of an external magnetic field aligns the spin of their charged particles, resulting in the material becoming a permanent magnet. In recent years, it was discovered that the application of an external magnetic field can also produce atom-sized cyclones of skyrmions, which act like baryon particles and can be moved coherently over macroscopic distances. These properties make skyrmions excellent candidates for spintronic applications.
Vortex structures occur in nature across a broad range of length scales
Vortex structures occur in nature across a broad range of length scales, from galaxies and weather systems all the way down to the atomic scale of polar vortices in ferroics.
„We believe the polar vortices we observed in ferroelectrics, when fully explored, have the potential to be topological states of matter that are similar to magnetic skyrmions,” Ramesh says. „The fact that our polar vortices can display emergent behavior in their electronic, optical, magnetic and other properties suggests that heretofore unexplored applications and functionalities could be possible.”
Ramesh, Martin and their collaborators worked with what has become a canonical system in the community, ultrafine layered structures built from lead titanate and strontium titante compounds controlled down to a few unit cells each, in which each unit cell is approximately 0.4 nanometers thick. They created superlattices that harbored a three-way competition between elastic, electrostatic and gradient energies within the layers of lead titanate and strontium titanate. This unique three-way competition gives rise to the polar vortices.
„As we tune the period lengths of our superlattices, we can tune the relative importance of these three energy scales,” Martin says. „Although rather exotic things can occur if one changes the superlattice period to be both smaller and bigger than we studied here, we really found the ‘sweet-spot’ in this work that produced these polar vortices which are an entirely new phenomenon.”
A combination of scanning transmission electron microscopy (STEM) and X-ray diffraction studies were used observe and characterize the polar vortices. The STEM work was carried out at Berkeley Lab’s Molecular Foundry, a DOE Office of Science User Facility, on TEAM 0.5, the world’s most powerful transmission electron microscope. The X-ray diffraction work was carried out at the Advanced Photon Source, another DOE Office of Science User Facility, which is hosted by DOE’s Argonne National Laboratory.
„Our study is really indicative of how DOE-funded research programs can bring together a diverse range of expertise, including atomically-controlled materials synthesis and cutting-edge research facilities, and materials theory to enable foundational discoveries that really change the way we think about exotic materials and the possibilities for using them,” says Ramesh.
„This is just the beginning for the study of polar vortices in ferroelectric materials,” Martin says. „We’re observing a new state of matter and we have our work cut out for us in mapping and understanding how it evolves. We can imagine adding a magnetic spin component to similar superlattices and thus potentially paving a pathway to fundamentally demonstrate electric-field control of magnetism.”
Source: By Lynn Yarris, Lawrence Berkeley National Laboratory
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Read more: Polar vortices observed in ferroelectric