Scientific Highlights from Research Division
Research with Neutrons and Muons (NUM)
With experimental work demonstrating that the correlated ground state of the pyrochlore system Ce2Sn2O7 is a quantum liquid of magnetic octupoles, an international team led by PSI researcher Romain Sibille establishes a fundamentally new state of matter: higher-rank multipole ice.
We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations.
Spin-based logic architectures provide nonvolatile data retention, near-zero leakage, and scalability, extending the technology roadmap beyond complementary metal–oxide–semiconductor logic. Architectures based on magnetic domain walls take advantage of the fast motion, high density, non-volatility and flexible design of domain walls to process and store information. Such schemes, however, rely on domain-wall manipulation and clocking using an external magnetic field, which limits their implementation in dense, large-scale chips.
At the ultracold neutron source at PSI, researchers have measured a property of the neutron more precisely than ever before: its electric dipole moment. That's because the search is still on for an explanation of why, after the Big Bang, there was more matter than antimatter.
Using a newly developed imaging method, researchers were able to visualise the magnetic structure inside a material with nanoscale resolution. They succeeded in creating a short "film" consisting of seven movie frames that shows, for the first time in 3D, how tiny vortices of the magnetisation deep within a material change over time.
We report a comprehensive muon spin rotation (μSR) study of the prototypical magnetoelectric antiferromagnet Cr2O3. We find the positively charged muon (μ+) occupies several distinct interstitial sites and displays a rich dynamic behavior involving local hopping, thermally activated site transitions, and the formation of a charge-neutral complex composed of a muon and an electron polaron.
Tunable anomalous Hall conductivity through volume-wise magnetic competition in a topological kagome magnet
Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, we explore magnetic correlations in the kagome magnet Co3Sn2S2. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound.
Possible room-temperature signatures of unconventional 4f-electron quantum criticality in YbMn6Ge6−xSnx
We investigate the Sn composition dependence of the Yb valence and local magnetization in YbMn6Ge6−xSnx (4.25 ≤x≤ 5.80) using x-ray absorption spectroscopy (XANES) and x-ray magnetic circular dichroism at the Yb L3 edge. In these materials, where Mn is ferromagnetically ordered, we observe a decrease of the Yb valence upon reducing the chemical pressure by Sn doping and a suppression of the Yb magnetic moment for strongly hybridized 4f states (ν ∼ 2.77).
Magnetism and anomalous transport in the Weyl semimetal PrAlGe: possible route to axial gauge fields
In magnetic Weyl semimetals, where magnetism breaks time-reversal symmetry, large magnetically sensitive anomalous transport responses are anticipated that could be useful for topological spintronics. The identification of new magnetic Weyl semimetals is therefore in high demand, particularly since in these systems Weyl node configurations may be easily modified using magnetic fields. Here we explore experimentally the magnetic semimetal PrAlGe, and unveil a direct correspondence between easy-axis Pr ferromagnetism and anomalous Hall and Nernst effects.
We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k⃗ magnetic phases below TN. The topological properties of a phase stable at intermediate magnetic fields parallel to the c axis are suggested by observation of a topological Hall effect.
Researchers in PSI's Laboratory for Scientific Computing and Modelling solve the most complex problems through a combination of theory, modelling, and high-performance computing. With powerful computers, they simulate the smallest molecules or large-scale research facilities.
Every folded protein presents an interface with water that is composed of domains of varying hydrophilicity/-phobicity. Many simulation studies have highlighted the nonadditivity in the wetting of such nanostructured surfaces in contrast with the accepted theoretical formula that is additive. We present here an experimental study on surfaces of identical composition but different organization of hydrophobic and hydrophilic domains.
Magnetic ground states with peculiar spin textures, such as magnetic skyrmions and multifunctional domains are of enormous interest for the fundamental physics governing their origin as well as potential applications in emerging technologies. Of particular interest are multiferroics, where sophisticated interactions between electric and magnetic phenomena can be used to tailor several functionalities.
Distortion mode anomalies in bulk PrNiO3: Illustrating the potential of symmetry-adapted distortion mode analysis for the study of phase transitions
The origin of the metal-to-insulator transition (MIT) in RNiO3 perovskites with R = trivalent 4f ion has challenged the condensed matter research community for almost three decades. A drawback for progress in this direction has been the lack of studies combining physical properties and accurate structural data covering the full nickelate phase diagram. Here we focus on a small region close to the itinerant limit (R = Pr, 1.5K < T < 300K), where we investigate the gap opening and the simultaneous emergence of charge order in PrNiO3.
Radionuclides open up new options for treating cancer. Christian Rüegg, head of the Research with Neutrons and Muons Division at PSI, explains the significance of the Swiss Spallation Neutron Source SINQ at PSI.
Artificial spin ices consist of nanomagnets arranged on the sites of various periodic and aperiodic lattices. They have enabled the experimental investigation of a variety of fascinating phenomena such as frustration, emergent magnetic monopoles and phase transitions that have previously been the domain of bulk spin crystals and theory, as we discuss in this Review.
Magnetic-Field Control of Topological Electronic Response near Room Temperature in Correlated Kagome Magnets
Strongly correlated kagome magnets are promising candidates for achieving controllable topological devices owing to the rich interplay between inherent Dirac fermions and correlation-driven magnetism. Here we report tunable local magnetism and its intriguing control of topological electronic response near room temperature in the kagome magnet Fe3Sn2 using small angle neutron scattering, muon spin rotation, and magnetoresistivity measurement techniques.
It is reminiscent of a paper bird made with the help of the Japanese folding art origami: a microrobot that uses the force of magnetic fields to move. In the future, such small machines could be used, for example, in medical operations.
Shape-morphing systems, which can perform complex tasks through morphological transformations, are of great interest for future applications in minimally invasive medicine, soft robotics, active metamaterials and smart surfaces. With current fabrication methods, shape-morphing configurations have been embedded into structural design by, for example, spatial distribution of heterogeneous materials, which cannot be altered once fabricated.
In addition to the Kitaev (K) interaction, candidate Kitaev materials also possess Heisenberg (J) and off- diagonal symmetric (Γ) couplings. We investigate the quantum (S=1/2) K-J-Γ model on the honeycomb lattice by a variational Monte Carlo method. In addition to the “generic” Kitaev spin liquid (KSL), we find that there is just one proximate KSL (PKSL) phase, while the rest of the phase diagram contains different magnetically ordered states.