Observation of Magnetoelectric Coupling

Multiferroic materials with coexisting ferroelectric and ferromagnetic orders have attracted much attention due to the magnetoelectric (ME) coupling opening prospects for alternative multifunctional electronic devices.  Switching magnetization by applied electric rather than magnetic field or spin-polarized current requires much less energy, making multiferroics promising for memory and logic applications. Due to a limited number of single-phase multiferroic compounds operating at room temperature, composite multiferroics containing ferroelectric and ferromagnetic components have been considered as viable alternatives. Moreover, it was shown that composite multiferroic materials often have much larger magnetoelectric coupling effect compared to their single-phase counterparts.

The recently emerged class of polycrystalline doped HfO2-based ferroelectric thin films, which are compatible with the modern Si technology, is a promising ferroelectric component in composite multiferroic heterostructures and it is therefore crucial to explore the ME effect at the ferroelectric/ferromagnetic interface in the heterostructures comprising doped HfO2. In this respect, a strong charge-mediated magnetoelectric coupling at the interface between classical ferromagnetic metal – Ni and ferroelectric HfO2has been recently predicted by theoretical modelling.

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Image: Schematic drawing of a single capacitor device structure used in operando XAS/XMCD and HAXPES/MCDAD measurements with EELS (Electron energy loss spectroscopy) map of Co, Ni and O. Polarization vs. voltage hysteresis loop at RT and LT (left) and  MOKE (right) of Au/Co/Ni/HZO/W sample are also shown in figure.

Credit: Elettra

Activation of order-disorder dynamics in crystalline Buckybowls

Dibenzo[ghi,mno]Fluoranthene, akacorannulene (C20H10), is a peculiar bowl-shaped molecule displaying unusual pentagonal symmetry and building block of the most celebrated Buckminster Fullerene – C60


Its nanostructured arrangement together with the eminent dipole moment of 2.1 Debye and a high electron affinity, make this system largely appealing for its use in energy-related applications, such as in hydrogen storage, ion-batteries, or super-capacitors. Additionally, this molecule has been suggested to be a component of interstellar dusts.   
In this work, published in Carbon, an international group including researchers from Italy, United Kingdom, Spain, and China has brought to the fore the unexpectedly rich thermophysical behaviour of this system in the thermal range 200 – 600 K, not anticipated on the basis of previous studies.


Combining state-of-the-art synchrotron (MCX beamline, Elettra) and neutron (IRIS beamline, ISIS) scattering techniques, together with differential scanning calorimetry (DSC), for the first time a well defined pre-melting transition has been clearly identified starting at about 382 K, well below the melting point of 540 K, resulting in the progressive suppression of molecular and supramolecular order and associated to the emergence of rotor-like states, as highlighted by the decrease in the elastic intensity and the sizeable increase in the quasi-elastic scattering (see Fig 1b– showing a marked separation in temperature between the two regimes).  

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Image: Figure 1.  (a) Synchrotron powder diffraction and Rietveld refinement of the room temperature average structure of Corannulene. (b) Temperature dependent quasi-elastic (IQE) and elastic (Iel) fractions, highlighting the transition to the dynamic state.

Recycling alginate composites for thermal insulation

Thermal insulation materials represent one the most straightforward, yet effective, technologies for improving the energy efficiency of buildings (and not only) – one of the key strategies for reducing carbon emissions. Natural-based materials and downcycled industrial and agricultural waste, thanks to their potentially reduced environmental footprint, have already made their way up to the market with the aim of limiting the ever-growing waste stream generated by the industrial sector. Research efforts on the topic are currently mainly focused on developing new insulation solutions, in which waste is reconverted as a new valuable resource. Carbohydrates, such as alginate, cellulose or chitosanare currently extensively studied base materials for thermal insulation systems, in the form of aerogels or as low-impact binding agents in waste-filled panels. Unfortunately, little or no attention has been paid to the end-of-life fate of these recycled materials; disposal (or incineration) still represents the only available option. This unprofitable scenario is even more critical in the case of polysaccharide-based composites specifically developed to reuse industrial waste. 


This was the starting point of our work, mainly conducted at the laboratories of the Engineering and Architecture department of the University of Trieste, in collaboration with TomoLab at Elettra. We developed a recycling process for an alginate-based thermal insulation foam, in which the original material is fully recovered and the thermal and acoustic insulation performances are maintained. The original foam is produced via a patented process in which alginate is used as the host poly-anionic matrix for industrial fiberglass waste. 

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Image: SEM and μCT image of oCAF

Credit: Figure reprinted from Carbohydrate Polymers, 251, Matteo Cibinel, Giorgia Pugliese, Davide Porrelli, Lucia Marsich, Vanni Lughi, Recycling alginate composites for thermal insulation, 116995, Copyright 2021, with permission from Elsevier.

Unravelling the molecular structure, self-assembly, and properties of a cephalopod protein variant

Cephalopods, such as the loliginid in Figure 1A, are known for their remarkable ability to rapidly change the color and appearance of their skin. These capabilities are enabled in part by unique structural proteins called reflectins, which play essential roles in optical behavior of cephalopod skin cells. Moreover, reflectins have demonstrated exciting potential as functional materials within the context of biophotonic and bioelectronic systems. Given reflectins’ demonstrated significance from both fundamental biology and applications perspectives, some research effort has been devoted to resolving their three-dimensional (3D) structures. However, the peculiar sequence composition of reflectins has made them extremely sensitive to subtle changes in environmental conditions and prone to aggregation, thus significantly complicating the study of their structure-function relationships and precluding their definitive molecular-level structural characterization. In this work, we have elucidated the structure of a reflectin variant at the molecular level, demonstrated a robust methodology for controlling its assembly and optical properties.


We began our studies by rationally selecting a prototypical reflectin variant (RfA1TV) by using a bioinformatics-guided approach (Figure 1B). Next, we not only produced the variant in high yield and purity but also optimized conditions for maintaining this protein in a monomeric state (Figure 1C). We then probed the protein with small angle X-ray scattering (SAXS) using the Austrian SAXS beamline at the Elettra Synchrotron Laboratory in Trieste, Italy. For this purpose, a well-dispersed solution of RfA1TV was prepared in a low-pH buffer and transferred into a glass capillary, which was positioned in the path of an incident X-ray beam. The X-rays scattered by the solution-borne RfA1TV molecules formed a 2-D pattern on a Pilatus3 1M detector (Figure 1D). Subsequently, radial averaging and image calibration of the two-dimensional data furnished corresponding one-dimensional curves, which were further processed, analyzed, and correlated with other experiments to obtain insight into the protein’s geometry (Figure 1E).

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Image: (A) A camera image of a Doryteuthis pealeii squid. (B) An illustration of the selection of the prototypical truncated reflectin variant (RfA1TV) from full-length Doryteuthis pealeii reflectin A1. (C) A digital camera image of a solution of primarily monomeric RfA1TV (Upper) and a corresponding cartoon of RfA1TV monomers (Lower Inset). (D) An illustration of the SAXS analysis of the reflectin variant, wherein incident X-rays are scattered by the solution-borne proteins to furnish a corresponding scattering pattern. (E)The 3D structure of RfA1TV (random coils – gray, helices – orange, β-strands – purple). 

Credit: This figure has been adapted from M. J. Umerani*, P. Pratakshya* et al.Proc. Natl. Acad. Sci. U.S.A 117, 32891-32901 (2020).

Unusual reversibility of molecular break-up of PAHs

By combining the high-resolution x-ray photoelectron spectroscopy at the SuperESCA beamline of Elettra with density functional theory a group of scientists from Italy, UK, Denmark and Germany has shown that the process of hydrogen removal from pentacene molecules adsorbed on Ir(111) follows a reversible chemical route, which allows hydrogen re-attachment to the carbon nanoribbon formed after the thermally induced C–H bond break-up. The thermal dissociation taking place upon controlled annealing can be reversed by cooling the system at room temperature and in a hydrogen atmosphere.


Besides the novelty of the chemical process, this phenomenon could have interesting implications for molecular electronics and for the manipulation of graphene nanoribbons which are known to present higher electron/hole mobilities and better thermal transport when dehydrogenated. 

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The power of surfaces: getting meta-polyaniline from para-aminophenol

Within the relatively young research field of the on-surface Chemistry the catalytic properties of surfaces are used to synthesize new materials that are not accessible with other techniques; in particular, by wet chemistry conventional routes. Following this bottom-up strategy, surfaces can be used as suitable platforms for enabling the emergence of novel low-dimensional molecular networks. In synergistic contribution,para-aminophenol (p-AP) molecules are taken as precursors (building block) for the surface reaction. Within a multi-technique approach that includes STM, nc-AFM, STS, XPS, and DFT calculations, we have found that these molecules, when adsorbed on Pt(111) and upon a thermal stimulus, covalently react each other forming oligomers coupled in an unprecedented metaconfiguration.

STM and nc-AFM microscopies showed that starting from individual molecules and by annealing the surface, results in the formation of oligomer chains , while monitoring the thermal behavior of the p-AP/Pt(111) system by means of high-resolution XPS at the SuperESCA beamline of Elettra shed light on the chemical nature of the species present on the crystal surface in the steps which lead to the synthesis of meta-polyaniline oligomers.

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Disclosing the time evolution of magnetic chirality after an optical excitation

Chiral magnetic structures, such as spin spirals, chiral domain walls and skyrmions, are intensively investigated due to their fascinating properties such as potentially enhanced stability and efficient spin-orbit torque driven dynamics. These structures are stabilized by the Dzyaloshinskii-Moriya interaction (DMI) that favours a chiral winding of the magnetisation.Cir

In a recent work, circularly polarized light pulses of the FERMI free-electron laser (FEL) has been used to disclose the dynamics of chiral order on ps time scale. After an optical excitation, the researchers observe a faster recovery of the chirality within the domain walls compared to the ferromagnetic order in the domains. The study paves the way for future investigations of fundamental aspects such as, e.g., the dependence of the timescales of the chiral order build-up on the absolute strength of the DMI. The control of the DMI can finally allow the manipulation at ultrafast timescale of chiral topological objects such as skyrmions and pave the path to applications in the field of ultrafast chiral spintronics.

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Direct X-ray and electron-beam lithography of halogenated zeolitic imidazolate framework

Metal-organic frameworks (MOFs) offer disruptive potential in micro- and optoelectronics because of their chemical versatility and high porosity. For instance, the low dielectric constant (low-k) resulting from their porosity makes MOFs competitive candidates for high-performance insulators in future microchips. Both the MOF and microelectronics communities have been striving towards integrating MOFs in microchips, which requires two key engineering steps: thin film deposition and lithographic patterning. However, conventional lithography techniques use a sacrificial layer, so-called photoresist, to transfer a pattern into the desired material. The use of photoresist complicates the process, and might induce contamination of the highly porous MOF films. 


A group of researchers from KU Leuven (Belgium) coordinated by Rob Ameloot has used the deep X-ray lithography (DXRL) beamline at Elettra to demonstrate that MOFs can be patterned by X-ray lithography without the use of resist layer. The method is based on selective X-ray exposure of the MOF film, which induces chemical changes that enable its removal by a common solvent. This process completely avoids the resist layer, thus significantly simplifying patterning while maintaining the physicochemical properties of patterned MOFs intact. 

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Titanium defective sites in TS-1: structural insights by combining spectroscopy and simulation

Titanium Silicalite-1 (TS-1) is a titanium zeolite, whose peculiarity is the presence of Ti atoms isomorphously substituting the Si ones at tetrahedral framework positions. However, real TS-1 samples are characterized by the co-presence of other Ti sites, ranging from extended TiO2phases down to defective Ti sites. The “defective Ti” label covers a broad range of possible Ti moieties, whose structural description is in most of the cases barely qualitative in the literature. In this work, we combined experimental and theoretical approaches, aiming to unravel the exact structure of defective Ti sites. 

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A new tool in attosecond science

Measuring Angle-Resolved Phases in Photoemission

Photoionization is one of the earliest observations whose explanation led to the establishment of quantum mechanics. The process is fully described by few mathematical quantities—the probability amplitudes—that are of central interest in understanding the electronic structure of matter and its theoretical foundations. Probability amplitudes are complex numbers, which are described by a magnitude and a phase. Phase information (which can be equivalently expressed as a time, i.e., a fraction of the period of the light wave causing ionization) is lost in most measurements.

An international research team from Japan, Germany, Russia, Austria, Hungary, and the local team at the FERMI free-electron laser, combined two-color XUV photoelectron spectroscopy with real-time ab initio simulations to measure phase differences with a precision of few attoseconds. The measurements, in excellent agreement with calculations, revealed a significant anisotropy with the angle of observation of the outgoing photoelectron, particularly when the frequency of the light is nearly resonant with a transition in the atom.

“In atomic and molecular physics, the phase of probability amplitudes can reveal important information about phenomena such as the concerted motion of electrons (electron correlation) in chemical reactions” says Prof. Kevin Prince from Elettra – Sincrotrone Trieste “and our work provides a new tool for attosecond science, i.e., the observation in real time of the motion of electrons inside matter.”

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Image: Scheme of the experiment: Bichromatic, linearly polarized light (red and blue waves), with momentum kg and electric vector Eg, ionizes neon in the reaction volume. The electron wave packets (yellow and magenta waves) are emitted with electron momentum k. The averaged phase difference  between wave packets created by one- and two-photon ionization depends on the emission angle. The photoelectron angular distribution depends on the relative (optical) w‑2w phase f. Lower figures: Polar plots of photoelectron intensity at Ek=16.6 eV for coherent harmonics (asymmetric, colored plot) and incoherent harmonics (symmetric, gray plot).

Credit: Reproduced from You et al., Phys. Rev. X, 10, 031070 (2020) doi: 10.1103/PhysRevX.10.031070; copyright 2020 by the Authors. The original figure has been published under a Creative Commons Attribution 4.0 International license (CC BY 4.0) http://creativecommons.org/licenses/by/4.0/

Electron and X‑ray Focused Beam-Induced Cross-Linking in Liquids:

Toward Rapid Continuous 3D Nanoprinting and Interfacing using Soft Materials

Modern additive fabrication of three-dimensional (3D) micron to centimeter size constructs made of polymers and soft materials has immensely benefited from the development of photocurable formulations suitable for optical photolithography,holographic,and stereolithographymethods. Recent implementation of multiphoton laser polymerization and its coupling with advanced irradiation schemes has drastically improved the writing rates and resolution, which now approaches the 100 nm range. Alternatively, traditional electron beam lithography and its variations such as electron-beam chemical lithography, etc. rely on tightly focused electron beams and a high interaction cross-section of 0.1−10 keV electrons with the matter and have been routinely used for complex patterning of polymer resists, self-assembled monolayers, and dried gel films with up to a few nanometers accuracy.

Similarly, a significant progress has been made in deep X-ray lithography, direct writing with zone plate focused X-ray beams for precise, and chemically selective fabrication of high aspect ratio microstructures. Reduced radiation damage within the so-called “water window” has spurred wide biomedical X-ray spectroscopy, microscopy, and tomography research including material processing, for example, gels related controlled swelling and polymerization inside live systems, particles encapsulations,and high aspect ratio structures fabrication.The potential of focused X-rays for additive fabrication through the deposition from gas-phase precursors or from liquid solutions is now well recognized and is becoming an active area of research.

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Image: The electron/X-ray beam gelation in liquid polymer solution through a SiN ultrathin membrane. Varying the energy and focus of the soft X-rays smaller or larger excitation volumes and therefore finer or wider feature sizes and patterns can be generated.

Orbital angular momentum carried by an optical field can be imprinted onto a propagating electron wave

Photons have fixed spin and unbounded orbital angular momentum (OAM). While the former is manifested in the polarization of light, the latter corresponds to the spatial phase distribution of its wavefront. The distinctive way in which the photon spin dictates the electron motion upon light–matter interaction is the basis for numerous well-established spectroscopies. By contrast, imprinting OAM on a matter wave, specifically on a propagating electron, is generally considered very challenging and the anticipated effect undetectable.

We carried out an experiment at the LDM beam line at the FERMI free-electron laser, with the aim of inducing an OAM-dependent dichroic photoelectric effect on photo-electrons emitted by a sample of He atoms. The experiment involved a large international collaboration and surprisingly confirmed that the spatial distribution of an optical field with vortex phase profile can be imprinted coherently on a photoelectron wave packet that recedes from an atom. Our results explore new aspects of light–matter interaction and point to qualitatively novel analytical tools, which can be used to study, for example, the electronic structure of intrinsic chiral organic molecules. The results have been published in Nature Photonics.

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Image: A VUV free-electron laser (violet) is used to ionize a sample of He atoms, and an infrared beam (red) to imprint orbital angular momentum on photo-emitted electrons. Credit: J. Wätzel (Halle university)

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

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Image: a) Ni-3p core-level spectra collected from as-cleaved NiTe2 (black curves) and from the same surface exposed to 2·10L 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

Observation of flat bands in twisted bilayer graphene

Magic-angle materials represent a surprising recent physics discovery in double layers of graphene, the two-dimensional material made of carbon atoms in a hexagonal pattern. 

When the upper layer of two stacked layers of graphene is rotated by about 1 degree, the material suddenly turns into a superconductor. At a temperature of 3 Kelvin, this so-called twisted bilayer graphene (tbg) conducts electricity without resistance.

Now, an international team of scientists from Geneva, Barcelona, and Leiden have finally confirmed the mechanism behind this new type of superconductors. In Nature Physics, they show that the slight twist causes the electrons in the material to slow down enough to sense each other. This enables them to form the electron pairs which are necessary for superconductivity.

How can such a small twist make such a big difference? This is connected with moiré patterns, a phenomenon also seen in the everyday world. When two patterned fences are in front of another, one observes additional dark and bright spots, caused by the varying overlap between the patterns. Such moiré patterns (derived from the the French name of textile patterns made in a similar way) generally appear where periodical structures overlap imperfectly.

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Image: Angle resolved photoemission spectrum revealing flat non-dispersing electronic band filled with slow electrons separated by mini gaps from the rest of electronic structure in twisted bilayer graphene device.

Who stole the light?

Self-induced ultrafast demagnetization limits the amount of light diffracted from magnetic samples at soft x-ray energies.

Free electron X-ray lasers deliver intense ultrashort pulses of x-rays, which can be used to image nanometer-scale objects in a single shot. When the x-ray wavelength is tuned to an electronic resonance, magnetization patterns can be made visible. However, using increasingly intense pulses, the magnetization image fades away. The mechanism responsible for this loss in resonant magnetic scattering intensity has now been clarified.

A team of researchers from Max Born Institute Berlin (Germany), Helmholtz-Zentrum Berlin (Germany), Elettra Sincrotrone Trieste (Italy) and Sorbonne Université (France), has now precisely recorded the dependence of the resonant magnetic scattering intensity as a function of the x-ray intensity incident per unit area (the “fluence”) on a ferromagnetic domain sample. Via integration of a device to detect the intensity of every single shot hitting the actual sample area, they were able record the scattering intensity over three orders of magnitude in fluence with unprecedented precision, in spite of the intrinsic shot-to-shot variations of the x-ray beam hitting the tiny samples. The experiments with soft x-rays were carried out at the FERMI free-electron x-ray laser in Trieste, Italy.

In the results presented in the journal Physical Review Letters, the researchers show that while the loss in magnetic scattering in resonance with the Co 2p core levels has been attributed to stimulated emission in the past, for scattering in resonance with the shallower Co 3p core levels this process is not significant. The experimental data over the entire fluence range are well described by simply considering the actual demagnetization occurring within each magnetic domain, which the experimental team had previously characterized with laser-based experiments. Given the short lifetime of the Co 3p core, dominated by Auger decay, it is likely that the hot electrons generated by the Auger cascade, in concert with subsequent electron scattering events, lead to a reshuffling of spin up and spin down electrons transiently quenching the magnetization.

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Image:  Schematic sketch of the scattering experiment with two competing processes. The soft x-ray beam (blue line) hits the magnetic sample where it scatters from the microscopic, labyrinth-like magnetization pattern. In this process, an x-ray photon is first absorbed by a Co 3p core level (1). The resulting excited state can then relax either spontaneously (2), emitting a photon in a new direction (purple arrow), or by means the interaction with a second photon via stimulated emission (3). In this last case, the photons are emitted in the direction of the incident beam (blue arrow towards right). 

Liquid carbon can be disclosed if one is ultrafast enough

At the FERMI FEL, beamline EIS-TIMEX, a novel approach combining FEL and fs-laser radiation has been developed for generating liquid carbon under controlled conditions and monitoring its properties of at the atomic scale. The method has been put to the test depositing a huge amount (5 eV/atom, 40 MJ/kg) of optical energy delivered by an ultrashort laser pulse (less than 100 fs, 10-13 s) into a self-standing amorphous carbon foil (a-C, thickness about 80 nm) and subsequently probing the excited sample volume with the FEL pulse varying both the FEL photon energy across the C K-edge (~ 283 eV) and delay between FEL and laser. A time-resolved x-ray absorption spectroscopy (tr-XAS, Fig. 2a) has been obtained of l-C with a record time resolution of less than 100 fs.

This method allowed researchers to monitor the formation of the liquid carbon phase at a temperature of 14200 K and pressure of 0.5 Mbar occurring in about 300 fs after absorption of the laser pump pulse as an effect of the constant volume (isochoric) heating of the carbon sample.

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Image: Artistic image illustrating the ultrafast laser-heating process used to generate liquid carbon in the laboratory. Illustration: Emiliano Principi.