Tag: materials

The arrangement and interaction of magnetic moments of atoms

The arrangement and interaction of magnetic moments of atoms

In this study, researchers from a large international team including ANSTO, investigated the magnetic properties of two unique 2D triangular lattice antiferromagnetic materials (2D-TLHAF)* using various neutron scattering techniques. 

Multiferroic materials are being explored for use in advanced computers. Their quantum properties make them suitable for future computing applications, as they can manage and process the significantly larger volume of information more efficiently. Additionally, the unique properties of 2D magnets, such as flexibility and stackability, an ability to control layers of quantum devices or materials to create more efficient systems, have application in magnetism and spintronics.

The materials, hexagonal h-Lu0.3Y0.7MnO3 and h-Lu0.47Sc0.53FeO3, are a type of frustrated antiferromagnet, which means that the spins of the atoms in the material cannot all align in a way that minimises their energy due to the triangular arrangement of the lattice.

Lead author, instrument scientist Dr Shinichiro Yano said the materials exhibit fascinating and complex magnetic behaviours which has been difficult to investigate by conventional neutron scattering techniques.

Their unique magnetic properties and nontrivial quantum effects that can be observed and measured from the cold triple axis spectrometer Sikawith a setup of polarized neutrons and other neutron instruments at the Australian Centre for Neutron Scattering. 

The study, published in the American Physical Society Journal, reports two irreducible representations* to describe their magnetic structure. 

“These mathematical concepts help us understand how the magnetic moments (spins) of the atoms in these materials are arranged and how they interact with each other.”

Dr Andrew Manning, Helium-3 Polarisation instrument scientist said, “Polarized neutron scattering has shown that accurately describing the magnetic structures of a 2D-TLHAF requires the use of two irreducible representations, rather than relying on the assumption that the system undergoes spin reorientation when using only one irreducible representation.”

Read more on ANSTO website

New artificial intelligence method to create material ​‘fingerprints’

New artificial intelligence method to create material ​‘fingerprints’

Like people, materials evolve over time. They also behave differently when they are stressed and relaxed. Scientists looking to measure the dynamics of how materials change have developed a new technique that leverages X-ray photon correlation spectroscopy (XPCS), artificial intelligence (AI) and machine learning.

This technique creates ​“fingerprints” of different materials that can be read and analyzed by a neural network to yield new information that scientists previously could not access. A neural network is a computer model that makes decisions in a manner similar to the human brain.

In a new study by researchers in the Advanced Photon Source (APS) and Center for Nanoscale Materials (CNM) at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, scientists have paired XPCS with an unsupervised machine learning algorithm, a form of neural network that requires no expert training. The algorithm teaches itself to recognize patterns hidden within arrangements of X-rays scattered by a colloid — a group of particles suspended in solution. The APS and CNM are DOE Office of Science user facilities.

“The goal of the AI is just to treat the scattering patterns as regular images or pictures and digest them to figure out what are the repeating patterns. The AI is a pattern recognition expert.” — James (Jay) Horwath, Argonne National Laboratory

“The way we understand how materials move and change over time is by collecting X-ray scattering data,” said Argonne postdoctoral researcher James (Jay) Horwath, the first author of the study.

These patterns are too complicated for scientists to detect without the aid of AI. ​“As we’re shining the X-ray beam, the patterns are so diverse and so complicated that it becomes difficult even for experts to understand what any of them mean,” Horwath said.

For researchers to better understand what they are studying, they have to condense all the data into fingerprints that carry only the most essential information about the sample. ​“You can think of it like having the material’s genome, it has all the information necessary to reconstruct the entire picture,” Horwath said.

The project is called Artificial Intelligence for Non-Equilibrium Relaxation Dynamics, or AI-NERD. The fingerprints are created by using a technique called an autoencoder. An autoencoder is a type of neural network that transforms the original image data into the fingerprint — called a latent representation by scientists — and that also includes a decoder algorithm used to go from the latent representation back to the full image.

The goal of the researchers was to try to create a map of the material’s fingerprints, clustering together fingerprints with similar characteristics into neighborhoods. By looking holistically at the features of the various fingerprint neighborhoods on the map, the researchers were able to better understand how the materials were structured and how they evolved over time as they were stressed and relaxed.

AI, simply put, has good general pattern recognition capabilities, making it able to efficiently categorize the different X-ray images and sort them into the map. ​“The goal of the AI is just to treat the scattering patterns as regular images or pictures and digest them to figure out what are the repeating patterns,” Horwath said. ​“The AI is a pattern recognition expert.”

Using AI to understand scattering data will be especially important as the upgraded APS comes online. The improved facility will generate 500 times brighter X-ray beams than the original APS. ​“The data we get from the upgraded APS will need the power of AI to sort through it,” Horwath said.

Read more on Argonne website

Image: The AI-NERD model learns to produce a unique fingerprint for each sample of XPCS data. Mapping fingerprints from a large experimental dataset enables the identification of trends and repeating patterns which aids our understanding of how materials evolve.

Credit: Argonne National Laboratory.

Mechanisms of electrical switching in antiferromagnets

Mechanisms of electrical switching in antiferromagnets

The electronic devices we use on a day-to-day basis are powered by electrical currents. Data processing and computation also relies on information provided by electrons. This is what we call electronics. In recent years, a new field called spintronics emerged to overcome the limitations of traditional electronics, offering a leap towards high-density data storage and ultrafast computing dynamics. Spintronics employs a different concept. Instead of store information using the charge of electrons of the materials, the spintronic approach is to exploit their magnetic moment, in other words, their spin, to store and process information – aiming to make the computers of the future more compact, fast, and sustainable.

Antiferromagnets are considered very promising materials for future spintronic applications, offering unique properties to overcome limitations posed by current systems using ferromagnets. Lack of stray fields favor denser packing and high internal frequencies could allow faster operation. However, these properties at the same time make it more difficult to operate in terms of writing information, i.e. the switching part.

Now, a study lead by researchers from the Johannes Gutenberg University Mainz (Germany), in collaboration with the Tohoku University, the University of Tokyo (Japan) and the ALBA Synchrotron aims to understand the underlying antiferromagnetic switching mechanisms. The study disentangles two different switching mechanisms in an antiferromagnet material -cobalt (II) oxide or CoO- when subjected to a current pulse. One is due to the fundamental spin-orbit torque and the other is a heat-induced thermomagnetoelastic effect.


Read more on the ALBA website

Image: XMLD-PEEM imaging of cobalt (II) oxide (CoO) sample after the application of high current-density pulses along different directions, revealing two different switching mechanisms. Images obtained at CIRCE beamline of the ALBA Synchrotron.

Superstore MXene: New proton hydration structure determined

Superstore MXene: New proton hydration structure determined

MXenes are able to store large amounts of electrical energy like batteries and to charge and discharge rather quickly like a supercapacitor. They combine both talents and thus are a very interesting class of materials for energy storage. The material is structured like a kind of puff pastry, with the MXene layers separated by thin water films. A team at HZB has now investigated how protons migrate in the water films confined between the layers of the material and enable charge transport. Their results have been published in the renowned journal Nature Communications and may accelerate the optimisation of these kinds of energy storage materials.

One of the biggest challenges for a climate-neutral energy supply is the storage of electrical energy. Conventional batteries can hold large amounts of energy, but the charging and discharging processes take time. Supercapacitors, on the other hand, charge very quickly but are limited in the amount of stored energy. Only in the last few years has a new class of materials been discussed that combines the advantages of batteries with those of supercapacitors, named pseudocapacitors.

Promising materials: Pseudocapacitors

Among pseudocapacitive materials, so-called MXenes consisting of a large family of 2D transition metal carbides and nitrides appear particularly promising. Their structure resembles a puff pastry, with the individual layers separated by a thin film of water that enables the transport of charges. Titanium carbide MXenes, especially, are conductive and their layered structure combined with highly negatively-charged hydrophilic surfaces offers a unique material in which positively charged ions such as protons can diffuse very efficiently. The MXenes used in this study were synthesized in the group of Prof. Yury Gogotsi in Drexel University, USA.

Charge transport examined

Over the last years, this property has been used to store and release energy from protons at unprecedented rates in acidic environment. It remains though unclear if the charges are mostly stored based on proton adsorption at the MXene surface or through desolvation of proton in the MXene interlayer.

Confinement effect expected

Due to its two-dimensional geometry, the 2-3 layer thick water film trapped between the MXene layers is expected to solvate protons differently from bulk water that we classically know. While this confinement effect is supposed to play a role in the fast diffusion of protons inside MXene materials, it has been impossible until now to characterise protons inside a MXene electrode during charging and discharging.

Vibrational modes analysed

The team led by Dr. Tristan Petit at HZB has now succeeded in doing this for the first time by analysing vibrational modes of protons excited by infrared light. Postdoctoral researcher Dr Mailis Lounasvuori has developed an operando electrochemical cell that she used to analyse protons and water inside titanium carbide MXenes at BESSY II during the charging and discharging processes. In the process, she also succeeded in distilling out the special signature of the protons in the confined water between the MXene layers.

Read more on the HZB website

Image: The experiment: Infrared light excites protons in the water film, which move between the Ti3C2-MXene layers. Their oscillation patterns show that they behave differently than in a thicker film of water.

Credit: © M. Künsting /HZB

Revealing the thermal heat dance of magnetic domains

Revealing the thermal heat dance of magnetic domains

Scientists invented a new way of tracking electronic properties inside materials, and used it to visualize magnetic domains in a previously unseen way.

Everyone knows that holding two magnets together will lead to one of two results: they stick together, or they push each other apart. From this perspective, magnetism seems simple, but scientists have struggled for decades to really understand how magnetism behaves on the smallest scales. On the near-atomic level, magnetism is made of many ever-shifting kingdoms—called magnetic domains—that create the magnetic properties of the material. While scientists know these domains exist, they are still looking for the reasons behind this behavior.

Now, a collaboration led by scientists from the U.S. Department of Energy’s Brookhaven National Laboratory, Helmholtz-Zentrum Berlin (HZB), the Massachusetts Institute of Technology (MIT), and the Max Born Institute (MBI) published a study in Nature in which they used a novel analysis technique—called coherent correlation imaging (CCI)—to image the evolution of magnetic domains in time and space without any previous knowledge. The scientists could not see the “dance of the domains” during the measurement but only afterward, when they used the recorded data to “rewind the tape.”

The “movie” of the domains shows how the boundaries of these domains shift back and forth in some areas but stay constant in others. The researchers attribute this behavior to a property of the material called “pinning.” While pinning is a known property of magnetic materials, the team could directly image for the first time how a network of pinning sites affects the motion of interconnected domain walls.

“Many details about the changes in magnetic materials are only accessible through direct imaging, which we couldn’t do until now. It’s basically a dream come true for studying magnetic motion in materials,” said Wen Hu, scientist at the National Synchrotron Light Source II (NSLS-II) and co-corresponding author of the study.

Read more on the Brookhaven National Laboratory website

Image: The image shows the areas where the borders of magnetic domains accumulate over time. It is similar to a photo of a traffic intersection taken at night with a long exposure time. In such a photo, we would see brighter areas along the paths that most cars’ headlights traveled. Here we see brighter areas where most domain walls come together.

Understanding how motor proteins shape our cells

Understanding how motor proteins shape our cells

Understanding the busy networks inside our cells can help researchers develop new cancer treatments and prevent dangerous fungal infections.

With the help of the Canadian Light Source (CLS) at the University of Saskatchewan, a research team led by John Allingham from Queen’s University and Hernando Sosa from the Albert Einstein College of Medicine has shed light on a protein that regulates the intricate microscopic networks that give cells their shape and helps ship important molecules to diverse locations.

Using the CMCF beamline at the CLS and the cryo-EM facility at the Simons Electron Microscopy Center (SEMC) at the New York Structural Biology Center, the team found the missing pieces of an important puzzle.

In their published work, they are the first group to clearly describe the mechanism of action of a tiny motor protein called Kinesin-8 that enables it to control the structures of microtubule fiber networks inside the cell.

Read more on the CLS website

Image: Cells, Canadian Light Source.

X-ray microscopy with 1000 tomograms per second

X-ray microscopy with 1000 tomograms per second

Tomoscopy is an imaging method in which three-dimensional images of the inside of materials are reconstructed in rapid succession. A new world record has now been set at the Swiss Light Source at the Paul Scherrer Institute: with 1000 tomograms per second, it is now possible to non-destructively capture very fast processes and structural changes in materials on the micrometre scale, such as the burning of a sparkler or the foaming of a metal alloy for the production of stable lightweight materials. 

Most people are familiar with computed tomography from medicine: a part of the body is X-rayed from all sides and a three-dimensional image is then calculated, from which any sectional images can be created for diagnosis.

This method is also very useful for material analysis, non-destructive quality testing or in the development of new functional materials. However, to examine such materials with high spatial resolution and in the shortest possible time, the particularly intense X-ray light of a synchrotron light source is required. In the synchrotron light, even rapid changes and processes in material samples can be visualised if it is possible to capture 3-dimensional images in a very short time sequence.

A team led by Francisco García Moreno from the Helmholtz Centre Berlin is working on this, together with researchers from the Swiss Light Source SLS at the Paul Scherrer Institute (PSI). Two years ago, they managed a record 200 tomograms per second, calling the method of fast imaging “tomoscopy”. Now the team has achieved a new world record: with 1000 tomograms per second, they can now record even faster processes in materials or during the manufacturing process. This is achieved without any major compromises in the other parameters: the spatial resolution is still very good at several micrometres, the field of view is several square millimetres and continuous recording periods of up to several minutes are possible.

Read more on the PSI website

Also on the HZB website

Image: Christian Schlepütz at the Tomcat beamline of the Swiss Light Source SLS, where a team of scientists have developed a 3D imaging method capable of recording 1,000 tomograms per second.

Credit: Paul Scherrer Institute/Mahir Dzambegovic

Tuning the magnetic anisotropy of lanthanides

Tuning the magnetic anisotropy of lanthanides

The magnetism of lanthanide-directed nanoarchitectures on surfaces can be drastically affected by small structural changes. The study carried out in a collaboration between researchers from IMDEA Nanociencia and BOREAS beamline at ALBA reports the effect of the coordination environment in the reorientation of the magnetic easy axis of dysprosium-directed metal-organic networks on Cu(111). The authors show that the magnetic anisotropy of lanthanide elements on surfaces can be tailored by specific coordinative metal-organic protocols.

Recent findings have highlighted the potential of lanthanides in single atom magnetism. The stabilization of single atom magnets represents the ultimate limit on the reduction of storage devices. However, single standing atoms adsorbed on surfaces are not suitable for practical applications due to their high diffusion, i.e., low thermal stability. The next step towards more realistic systems is the coordination of these atoms in metal-organic networks.In 4f elements, the spin-orbit coupling (SOC) is larger than the crystal field, which might result in higher anisotropies. Furthermore, the crystal field acts as a perturbation of the SOC and can be tailored to increase the anisotropy by choosing an appropriate coordination environment. The strong localization of the 4f states reduces the hybridization with the surface, increasing the spin lifetimes, which is crucial, since a long magnetic relaxation time is mandatory for technological applications.

Read more on the ALBA website

Image: Cover picture showing the structure of the Dy-TPA network where C, H, O and Dy atoms are represented by black, red and green balls, respectively, the tilted orientation of the magnetic easy axis is represented by green arrows. 

Credit: ALBA

When vibrations increase on cooling: Anti-freezing observed

When vibrations increase on cooling: Anti-freezing observed

An international team has observed an amazing phenomenon in a nickel oxide material during cooling: Instead of freezing, certain fluctuations actually increase as the temperature drops. Nickel oxide is a model system that is structurally similar to high-temperature superconductors. The experiment, which was carried out at the Advanced Light Source (ALS) in California, shows once again that the behaviour of this class of materials still holds surprises.

In virtually all matter, lower temperatures mean less movement of its microscopic components. The less heat energy is available, the less often atoms change their location or magnetic moments their direction: they freeze. An international team led by scientists from HZB and DESY has now observed for the first time the opposite behaviour in a nickel oxide material closely related to high-temperature superconductors. Fluctuations in this nickelate do not freeze on cooling, but become faster.

Read more on the HZB website

Image: The development of this speckle pattern over time reveals microsocopic fluctuations in the material.

Credit: © 10.1103/PhysRevLett.127.057001

The performance of materials in extreme environments

The performance of materials in extreme environments

Key Points

  • Understanding how materials will perform in extreme environments is crucial to the development of new energy technologies, Australia’s defence capabilities and space exploration
  • ANSTO are leaders in the characterisation of materials from the atomistic to macroscopic scales. This is needed to fully understand performance and service life in extreme environments
  • ANSTO has world-leading infrastructure and materials research expertise to characterise materials for extreme environments

ANSTO researchers investigate how materials behave in extreme environments, providing information that is vital to support the development of our industries.

Extreme environments include situations where materials are exposed to a combination of different conditions, including high temperature, radiation, corrosion and mechanical load.

Read more on the ANSTO website

image: A/Prof Ondrej Muransky describes the capabilities at ANSTO to research materials that operate in extreme environments, such as nuclear reactors

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Recently, transition-metal dichalcogenides hosting topological states have attracted considerable attention for their potential implications for catalysis and nanoelectronics. The investigation of their chemical reactivity and ambient stability of these materials is crucial in order to assess the suitability of technology transfer. With this aim, an international team of researchers from Italy, Russia, China, USA, India, and Taiwan has studied physicochemical properties of NiTe2 by means of several experimental techniques and density functional theory. Surface chemical reactivity and ambient stability were followed by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) experiments at the BACH beamline, while the electronic band structure was probed by spin- and angle-resolved photoelectron spectroscopy (spin-ARPES) at the APE-LE beamline. 

Read more on the Elettra website

Image: a) Ni-3p core-level spectra collected from as-cleaved NiTe2 (black curves) and from the same surface exposed to 2·104 L of CO (red curves), H2O (green curves) and O2 (blue curves).  Credit: Adapted from “S. Nappini et al., Adv. Funct. Mater. 30, 2000915 (2020); DOI: 10.1002/adfm.202000915” with permission from Wiley (Copyright 2020) with license 4873681106527

Lab Resolves Origin of Perovskite Instability

Lab Resolves Origin of Perovskite Instability

The following news release was originally issued by Princeton University. The story describes how researchers investigated the inorganic perovskite, cesium lead iodide, that has attracted wide attention for its potential in creating highly efficient solar cells. The researchers used x-ray diffraction performed at Princeton University and x-ray pair distribution function measurements performed at the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Brookhaven National Laboratory, to find the source of thermodynamic instability in the perovskite. For more information about Brookhaven’s role in this research, please reach out to Cara Laasch, laasch@bnl.gov.  

Researchers in the Cava Group at the Princeton University Department of Chemistry have demystified the reasons for instability in an inorganic perovskite that has attracted wide attention for its potential in creating highly efficient solar cells.

Using single crystal X-ray diffraction performed at Princeton University and X-ray pair distribution function measurements performed at the Brookhaven National Laboratory, Princeton Department of Chemistry researchers detected that the source of thermodynamic instability in the halide perovskite cesium lead iodide (CsPbI3) is the inorganic cesium atom and its “rattling” behavior within the crystal structure.

Read more on NSLS II website

Image: Milinda Abeykoon, one of the lead beamline scientists at Brookhaven Lab, in preparation of the challenging experiments with Robert Cava’s team.

A scalable platform for two-dimensional metals

A scalable platform for two-dimensional metals

SCIENTIFIC ACHIEVEMENT

Using a new method for stabilizing a two-dimensional (2D) metal on a large-area platform, researchers probed the origins of the material’s superconductivity at the Advanced Light Source (ALS).

SIGNIFICANCE AND IMPACT

The work represents a notable milestone in advancing 2D materials toward broad applications in topological computing, advanced optics, and molecular sensing.

Expanding the scientific palette

If you confine everyday metals to layers only a few atoms thick, they acquire new properties that are different from those exhibited by their more common bulk forms. The ability to synthesize such two-dimensional (2D) metals means that the range of materials available for novel uses can be expanded to different areas of the periodic table—providing a much richer “scientific palette” of properties for applications in topological computing, advanced optics, and molecular sensing.

Read more on the ALS website

Image: A confined layer of metal atoms (silver spheres) on a silicon carbide (SiC) substrate is capped by a layer of graphene, allowing for new forms of low-dimensional metals with unique properties. Gold spheres represent Cooper pairs, responsible for conventional superconductivity. 

Credit: Yihuang Xiong/Penn State

In search of the lighting material of the future

In search of the lighting material of the future

At the Paul Scherrer Institute PSI, researchers have gained insights into a promising material for organic light-emitting diodes (OLEDs). The substance enables high light yields and would be inexpensive to produce on a large scale – that means it is practically made for use in large-area room lighting. Researchers have been searching for such materials for a long time. The newly generated understanding will facilitate the rapid and cost-efficient development of new lighting appliances in the future. The study appears today in the journal Nature Communications.

The compound is a yellowish solid. If you dissolve it in a liquid or place a thin layer of it on an electrode and then apply an electric current, it gives off an intense green glow. The reason: The molecules absorb the energy supplied to them and gradually emit it again in the form of light. This process is called electroluminescence. Light-emitting diodes are based on this principle.

Read more on the Swiss FEL and Swiss Light Source website

Image: Grigory Smolentsev in front of SwissFEL

Credit: Paul Scherrer Institute/Mahir Dzambegovic

Seeing “under the hood” in batteries

Seeing “under the hood” in batteries

From next-gen smartphones to longer-range electric cars and an improved power grid, better batteries are driving tech innovation. And to push batteries beyond their present-day performance, researchers want to see “under the hood” to learn how the individual ingredients of battery materials behave beneath the surface.

This could ultimately lead to battery improvements such as increased capacity and voltage.

But many of the techniques scientists use can only scratch the surface of what’s at work inside batteries, and a high-sensitivity X-ray technique at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is attracting a growing group of scientists because it provides a deeper, more precise dive into battery chemistry.

>Read more on the Advaced Light Source at LBNL website

Image: The high-efficiency RIXS system at the Advanced Light Source’s Beamline 8.0.1
Credit: Marilyn Sargent/Berkeley Lab

Preparation and characterization of mesoscale single crystals

Preparation and characterization of mesoscale single crystals

What did the Scientists Discover?
Single crystals are materials with periodic structure that extends across macroscopic distances as a coherent lattice free of grain boundaries. By isolating and studying their properties, bulk single crystals have revolutionized our fundamental understanding of materials from semiconductors to biomacromolecules, fueling innovations from microelectronic devices to pharmaceutical compounds. In contrast, our understanding of many mesostructured materials is still in its infancy in part due to the lack of available single crystals. Block copolymer self-assembly of mesostructured systems presented here is a promising method to prepare periodic 10–100 nm structures with coherent orientation over macroscopic lengths enabling their study.

Why is this important?
The method presented here can prepare macroscopic bulk single crystals with other block copolymer systems, suggesting that the method is broadly applicable to block copolymer materials assembled by solvent evaporation. It is expected that such bulk single crystals will enable fundamental understanding and control of emergent mesostructure-based properties in block-copolymer-directed metal, semiconductor, and superconductor materials.

>Read more on the CHESS website

Image: (extract, full image see here) Representative SAXS patterns with log scale colors from locations as indicated in (c), exhibiting polycrystalline (e), multi-(three) crystalline (f), and single crystal (g) behavior. Diagonal bars across bottom are shadows from photodiode wire.