Data Science

Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet

We report an extraordinary pressure dependence of the magnetic interactions in the metal-organic system [CuF2(H2O)2]2 pyrazine. At zero pressure, this material realizes a quasi-two-dimensional spin-1/2 square-lattice Heisenberg antiferromagnet. By high-pressure, high-field susceptibility measurements we show that the dominant exchange parameter is reduced continuously by a factor of 2 on compression.

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ISNR honorary membership awarded to Eberhard Lehmann

The International Society for Neutron Radiology ISNR was founded in 1996 with the aim to organize regular conferences with the focus on the use of neutrons for imaging purposes. During the 11th World Conference on Neutron Radiography, held recently in Sydney (Australia) and organized by ANSTO, the Honorary Membership of ISNR was awarded to Eberhard Lehmann - in recognition to his contributions for the progress in the field of neutron imaging on national and international level. The Neutron Imaging and Activation Group NIAG of the LNS has been active member in ISNR from the very beginning. Presently and since 2014, Markus Strobl the head of NIAG is vice-president elected of ISNR – and was reelected recently until 2022. In addition, NIAG member Pavel Trtik is now representing PSI in the ISNR board until 2022.

Diamond: a gem for micro-optics

Our image of a diamond structure was published on the cover page of the September 2018 issue of the journal "Materials Today". The corresponding paper reports on the nano-frabrication of micro-optical elements in diamond.

Figure 1 (a) Transient relative x-ray intensity of the (1.5 0.5 0.5) superlattice reflection of Sr0.97Ca0.03TiO3 upon above bandgap excitation with 40 fs pulses Inset: STO crystal structure as seen along the c-axis. phi measures the antiferrodistortive rotation of the oxygen octahedra (exaggerated) and represents the order parameter. (b) Calculated energy change per STO cubic unit cell as a function of oxygen displacement u/u0 along the in-plane cubic crystal axes resulting from the octahedral rotation at …

Moving Atoms by Photodoping

Understanding how and how fast we can drive atoms to create a structural phase transition is of fundamental interest as it directly relates to many processes in nature. Here we show that a photoexcitation can drive a purely structural phase transition before the energy is relaxed in the material that corresponds to a “warmer” equilibrated state.

General framework explaining magnetoelectric inversion of domain patterns: one parameter contains the information about the domain pattern (bottom layer), and a second parameter (middle layer) can be switched. That switching leads then to an inversion of the entire pattern (top layer). (Image: Naëmi Leo)

Multiferroics turned upside down

Experiments demonstrating the inversion of entire domain patterns in multiferroic crystals highlight just how versatile this class of materials is, and indicate a route to exploring novel functionalities.

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Claire Donnelly dissertation research awards

In August 2018, Claire Donnelly was awarded the SPS Award in Computational Physics, sponsored by COMSOL, and the Werner Meyer-Ilse Memorial Award. We congratulate her on these awards as well as for the two awards received earlier this year: the ETH Medal for an outstanding doctoral thesis and the American Physical Society Richard L. Greene Dissertation Award, recognizing doctoral thesis research of exceptional quality and importance. These prizes are for her dissertation on “Hard X-ray Tomography of Three Dimensional Magnetic Structures”. Claire carried out her dissertation in the Laboratory for Mesoscopic Systems (ETH Zurich – Paul Scherrer Institute) in collaboration with the CXS group and the OMNY project, with experiments conducted at the cSAXS beamline, SLS, and Sebastian Gliga, a Marie Curie Fellow at the University of Glasgow. She will continue this research at the University of Cambridge with a Leverhulme Fellowship supported by the Newton Trust. We wish her every success! - Picture courtesy of the APS.

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Shang Gao receives SGN Young Scientist Prize

Dr. Shang Gao was awarded the Young Scientist Prize of the Swiss Neutron Scattering Society for his high quality thesis and neutron scattering investigation leading to the discovery of a spiral spin-liquid state in the compound MnSc2S4 and of fast monopole hopping rates in the spin-ice compounds CdEr2X4. The prize is sponsored by Swiss Neutronics and is awarded annualy to a young scientist in recognition of a notable scientific achievement in the form of a PhD thesis. The photo shows Shang together with the SGN president Prof. Henrik Ronnow during the prize ceremony.

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Claire Donnelly dissertation and research awards

In August 2018, Claire Donnelly was awarded the SPS Award in Computational Physics, sponsored by COMSOL, and the Werner Meyer-Ilse Memorial Award. We congratulate her on these awards as well as for two awards earlier on in the year: the ETH Medal for an outstanding doctoral thesis and the American Physical Society Richard L. Greene Dissertation Award, recognizing doctoral thesis research of exceptional quality and importance. These prizes are for her dissertation on “Hard X-ray Tomography of Three Dimensional Magnetic Structures”.

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Claire Donnelly dissertation research awards

Claire Donnelly, Mesoscopic Systems (ETH Zurich - PSI), was awarded the COMSOL SPS Award in Computational Physics, the Werner Meyer-Ilse Memorial Award, the ETH Medal for an outstanding doctoral thesis, and the American Physical Society Richard L. Greene Dissertation Award.

Anomalous Hall effect in Weyl semimetal half-Heusler compounds RPtBi (R = Gd and Nd)

GdPtBi and NdPtBi belong to the Heusler family of compounds and are conventional antiferromagnets below 9 and 2.1 K, respectively. We present evidence for magnetic-field–induced Weyl physics in these compounds, namely, a chiral anomaly (negative magnetoresistance) and an anomalous Hall effect (AHE) with a large anomalous Hall angle over a wide range of temperature. The AHE and chiral anomaly have a similar temperature dependence, indicating their common origin.

Magnetoelectric inversion of domain patterns

The inversion of inhomogeneous physical states has great technological importance; for example, active noise reduction relies on the emission of an inverted sound wave that interferes destructively with the noise of the emitter1, and inverting the evolution of a spin system by using a magnetic-field pulse enables magnetic resonance tomography2.

Modifying the contact angle of anisotropic cellulose nanocrystals: Effect on interfacial rheology and structure

Cellulose nanocrystals (CNC) are an emerging natural material with the ability to stabilize fluid/fluid interfaces. Native CNC is hydrophilic and does not change the inter- facial tension of the stabilized emulsion or foam system. In this study, rod-like cellulose particles were isolated from hemp and chemically modified to alter their hydrophobicity, i.e. their surface-activity, which was demonstrated by surface tension measurements of the particles at the air/water interface.

Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates

We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high- temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No kz dispersion is observed along the nodal direction, whereas a significant antinodal kz dispersion is identified for La-based cuprates.

The effective charge caused by Al–O monolayers as function of tunnel-SiO2 thickness and the normalized Al K edge XANES fluorescence yield (FY) spectra. Reprinted with permission from ACS Applied Materials& Interfaces, Copyright (2018) American Chemical Society

The negative charge density in Al-O monolayers on SiO2 surfaces

Single atomic layers of aluminum oxide embedded in SiO2 thin films, play an important role for the design of carrier-selective passivating contacts for high efficiency silicon based photovoltaic applications. Researchers from the Australian National University (ANU, Canberra, Australia), the Karlsruhe Institute of Technology (IT, Karlsruhe, Germany) and PSI have used synchrotron radiation to reveal the bonding configuration and local atomic surrounding of the Al-atoms in such surface oxide layers. The results corroborates theoretical calculations and contribute to a new model to explain the origin of the negative fixed charge in the Al-O/SiO2 stack, which has promising properties for a carrier-selective passivating contact for future silicon solar cells.

First serial femtosecond crystallography (SFX) pilot user experiment at SwissFEL

On the 7th to 12th of August 2018, a collaborative group of scientists from the Paul Scherrer Institute and members of the LeadXpro and Heptares pharmaceutical companies led by Karol Nass (PSI macromolecular crystallography MX-SLS group) performed the first serial femtosecond crystallography (SFX) pilot user experiment at the SwissFEL X-ray free electron laser (XFEL).

Pauling Entropy, Metastability, and Equilibrium in Dy2Ti2O7 Spin Ice

Determining the fate of the Pauling entropy in the classical spin ice material Dy2Ti2O7 with respect to the third law of thermodynamics has become an important test case for understanding the existence and stability of ice-rule states in general. The standard model of spin ice—the dipolar spin ice model—predicts an ordering transition at T ≈ 0.15K, but recent experiments by Pomaranski et al.

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Kinetics of Lifetime Changes in Bimetallic Nanocatalysts Revealed by Quick X‐ray Absorption Spectroscopy

The different reaction steps involved in repeated Pt13In9 segregation‐alloying are identified by XAS and kinetically characterized at the single‐cycle level.

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The SLS congratulates Ronald Frahm for receiving the IXAS outstanding achievement Award 2018

The highest award of the international X-ray absorption spectroscopy (IXAS) society, the Edward Stern Outstanding Achievement Award, was presented to Prof. Ronald Frahm during the tri-annual IXAS meeting in Kraków, Poland in July 2018.

Collective magnetism in an artificial 2D XY spin system

Two-dimensional magnetic systems with continuous spin degrees of freedom exhibit a rich spectrum of thermal behaviour due to the strong competition between fluctuations and correlations. When such systems incorporate coupling via the anisotropic dipolar interaction, a discrete symmetry emerges, which can be spontaneously broken leading to a low-temperature ordered phase.

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Simon Corrodi successfully defends his thesis on the Mu3e fibre detector

Simon Corrodi has made important contributions to all aspects of fibre detector development, ranging from simulation and reconstruction via fibre characterization and mechanical integration to data acquisition and electronics. He has now successfully defended his thesis at ETH Zürich.

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Structure of the Co(I) Intermediate of a Cobalt Pentapyridyl Catalyst for Hydrogen Evolution Revealed by Time‐Resolved X‐ray Spectroscopy

The mechanism of hydrogen evolution by cobalt polypyridyls catalysts is investigated. Pump-probe X‐ray absorption spectra measured at SuperXAS in the microsecond time range indicate that the pendant pyridine dissociates from the cobalt in the intermediate Co(I) state. This opens the possibility for pyridinium to act as an intramolecular proton donor, which can be used for the development of efficient catalysts.

Direct electric field control of the skyrmion phase in a magnetoelectric insulator

Magnetic skyrmions are topologically protected spin-whirls currently considered as promising for use in ultra-dense memory devices. Towards achieving this goal, exploration of the skyrmion phase response and under external stimuli is urgently required.

Araris Biotech among top 5 in business plan ranking at >>venture2018>>

Araris Biotech, a Spin-Off company in foundation from the Center for Radiopharmaceutical Sciences (Prof. Roger Schibli) at the BIO division, has been ranked in the TOP5 in the business plan competition of >>Venture>>(link is external). Araris is focusing on the development of a new method for the generation of antibody-drug conjugates (ADCs) with a well-defined, optimal antibody-to-drug ratio. The technology will be used to establish a drug development platform for targeted therapies and diagnostic applications. more info(link is external)