Connection between f-electron correlations and magnetic excitations in UTe2
The detailed anisotropic dispersion of the low-temperature, low-energy magnetic excitations of the candidate spin-triplet superconductor UTe2 is revealed using inelastic neutron scattering. The magnetic excitations emerge from the Brillouin zone boundary at the high symmetry Y and T points and disperse along the crystallographic b-axis. In applied magnetic fields ...
Small-angle scattering interferometry with neutron orbital angular momentum states
Methods to prepare and characterize neutron helical waves carrying orbital angular momentum (OAM) were recently demonstrated at small-angle neutron scattering (SANS) facilities. These methods enable access to the neutron orbital degree of freedom which provides new avenues of exploration in fundamental science experiments as well as in material characterization applications.
However, ....
Operando phase mapping in multi-material laser powder bed fusion
Additive manufacturing (AM) or “3D printing” of metals, which builds structure layer by layer, has revolutionized the production of intricate 3D designs. Among its techniques, laser powder bed fusion (PBF-LB) excels in creating metallic parts with intricate designs and high precision. This process can combine different metals into innovative multi-material components with tailored properties, with regards to e.g., strength and thermal conductivity, surpassing the capabilities of single-material designs. However, ....
Continuum Excitations in a Spin Supersolid on a Triangular Lattice
Magnetic, thermodynamic, neutron diffraction and inelastic neutron scattering are used to study spin correlations in the easy-axis XXZ triangular lattice magnet K2Co(SeO3)2. Despite the presence of quasi-2D “supersolid” magnetic order, the low-energy excitation spectrum contains no sharp modes and is instead a broad and structured multiparticle continuum. Applying a weak magnetic field ...
Reentrant multiple-q magnetic order and a “spin meta-cholesteric” phase in Sr3Fe2O7
Topologically nontrivial magnetic structures such as skyrmion lattices are well known in materials lacking lattice inversion symmetry, where antisymmetric exchange interactions are allowed. Only recently, topological multi-q magnetic textures that spontaneously break the chiral symmetry, for example, three-dimensional hedgehog lattices, were discovered in centrosymmetric compounds, where they are instead driven by frustrated interactions. Here we show that ...
Ferromagnetic quantum critical point protected by nonsymmorphic symmetry in a Kondo metal
Quantum critical points (QCPs), zero-temperature phase transitions, are win- dows to fundamental quantum-mechanical phenomena associated with universal behaviour. Magnetic QCPs have been extensively investigated in the vicinity of antiferromagnetic order. However, QCPs are rare in metallic ferromagnets due to the coupling of the order parameter to electronic soft modes. Recently, antisymmetric spin-orbit coupling in noncentrosymmetric systems was suggested to protect ferromagnetic QCPs. Nonetheless, multiple centrosymmetric materials ...
Room temperature magnetoelectric magnetic spirals by design
Frustrated magnets with ordered magnetic spiral phases that spontaneously break inversion symmetry have received significant attention from both fundamental and applied sciences communities due to the experimental demonstration that some of these materials can couple to the lattice and induce electric polarization. In these materials, the common origin of the electric and magnetic orders guarantees substantial coupling between them, which is highly desirable for applications ...
Magnetostructural Coupling at the Néel Point in YNiO3 Single Crystals
The recent discovery of superconductivity in infinite layer thin films and bulk Ruddlesden–Popper nickelates has stimulated the investigation of other predicted properties of these materials. Among them, the existence of magnetism-driven ferroelectricity in the parent compounds RNiO3 (R = 4f lanthanide and Y) at the onset of the Néel order, TN, has remained particularly elusive. Using diffraction techniques, we reveal here the existence of magnetostriction at TN in bulk YNiO3 single crystals. Interestingly, the associated lattice anomalies ...
Conventional superconductivity in the doped kagome superconductor Cs(V0.86Ta0.14)3Sb5 from vortex lattice studies
A hallmark of unconventional superconductors is a complex electronic phase diagram where intertwined orders of charge-spin-lattice degrees of freedom compete and coexist. While the kagome metals such as CsV3Sb5 also exhibit complex behavior, involving coexisting charge density wave order and superconductivity, much is unclear about the microscopic origin of the superconducting pairing. We study the vortex lattice in the superconducting state of Cs(V0.86Ta0.14)3Sb5, where the Ta-doping suppresses charge order and enhances superconductivity. Using small-angle neutron scattering ...
Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe3
Van-der-Waals magnetic materials can be exfoliated to realize ultrathin sheets or interfaces with highly controllable optical or spintronics responses. In majority, these are collinear ferro-, ferri-, or antiferromagnets, with a particular scarcity of lattice-incommensurate helimagnets of defined left- or right-handed rotation sense, or helicity. Here, we report polarized neutron scattering experiments on DyTe3, whose layered structure has highly metallic tellurium layers separated by double-slabs of dysprosium square nets...
Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet
Emergent quasiparticles with a Dirac dispersion in condensed matter systems can be described by the Dirac equation for relativistic electrons, in analogy with Dirac particles in high-energy physics. For example, electrons with a Dirac dispersion have been intensively studied in electronic systems such as graphene and topological insulators. However, charge is not a prerequisite for Dirac fermions, and the emergence of Dirac fermions without a charge degree of freedom has been theoretically predicted to be realized in Dirac quantum spin liquids. These quasiparticles ...
Electron Glass Phase with Resilient Zhang-Rice Singlets in LiCu3O3
LiCu3O3 is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3d9) are sandwiched in between planes of Cu(I) (3d10) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu dz2/O pz derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3dx2−y2/O 2px,y derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes.
A precision mechanical masterpiece in miniature
With the discovery of a golden miniature box lock, an extraordinary and unique archaeological find was made in north-western Germany by a licensed detectorist.
The object represents an extremely reduced and valuable version of the provincial Roman box locks. These everyday objects were in general significantly larger and normally made either of iron, iron with silver or bronze bands or bronze.
Field-induced bound-state condensation and spin-nematic phase in SrCu2(BO3)2 revealed by neutron scattering up to 25.9 T
In quantum magnetic materials, ordered phases induced by an applied mag- netic field can be described as the Bose-Einstein condensation (BEC) of mag- non excitations. In the strongly frustrated system SrCu2(BO3)2, no clear magnon BEC could be observed, pointing to an alternative mechanism, but the high fields required to probe this physics have remained a barrier to detailed investigation.Here we exploit the first purpose-built high-field neutron scattering facility to measure ...
Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular AFM Co1/3TaS2
The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120° structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wave- length limit of magnetic skyrmion crystals. We report the metallic TLAF Co1/3TaS2 as the first example of tetrahedral triple-Q magnetic ordering with the associated topological Hall effect (non-zero σxy(H = 0)). We also ...
Skyrmion metamorphosis: Lattice transitions of hybrid skyrmions in a polar magnet
Magnetic skyrmions, with their distinctive vortex-like magnetic spin configurations, continue to intrigue researchers due to their potential applications in nanoscience and technology. Traditionally skyrmions form two-dimensional hexagonal close-packed lattices, with the skyrmions themselves displaying one of just two types of internal magnetization texture known as Bloch- or Néel-type. Recent theories hinted at the prospect of reconfigurable transitions between skyrmion phases of different lattice types and internal textures. Until now, experimental evidence supporting such theories has been scarce.
Cobalt-free layered perovskites RBaCuFeO5+d (R = 4f lanthanide) as electrocatalysts for the oxygen evolution reaction
Co oxides with perovskite-related structure are particularly promising, cost-effective OER catalysts. However, the increasing Co demand by the battery industry is pushing the search for Co-free alternatives. Here we investigate the potential of the Co-free layered perovskite family RBaCuFeO5+δ (R = 4f lanthanide), where we identify the critical structural and electronic variables leading to high OER catalytical performance. The employed methodology, based in the use of advanced neutron and X-ray synchrotron techniques combined with ab initio DFT calculations allowed to reveal LaBaCuFeO5+δ as new, promising Co-free electroctalyst. Moreover, we could show that this material can be industrially produced in nanocrystalline form. We believe that the reported results and methodology may contribute to the implementation of new technologies aimed to generate energy with lower carbon emissions, and can also inspire the scientific community in their search of other Co-free materials with good OER electrocatalytical properties.
Integrative solution structure of PTBP1-IRES complex reveals strong compaction and ordering with residual conformational flexibility
RNA-binding proteins (RBPs) are crucial regulators of gene expression, often composed of defined domains interspersed with flexible, intrinsically disordered regions. Determining the structure of ribonucleoprotein (RNP) complexes involving such RBPs necessitates integrative structural modeling due to their lack of a single stable state. In this study, we integrate magnetic resonance, mass spectrometry, and small-angle scattering data to determine the solution structure of ...
Direct observation of topological magnon polarons in a multiferroic material
Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe2Mo3O8 possessing strong magnon-phonon coupling.
Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe2
Fifty years after Anderson’s resonating valence-bond proposal, the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) remains the ultimate platform to explore highly entangled quantum spin states in proximity to magnetic order. Yb-based delafossites are ideal candidate TLHAF materials, which allow experimental access to the full range of applied in-plane magnetic fields. We perform a systematic neutron scattering study of CsYbSe2, first proving the Heisenberg character of the interactions and quantifying the second-neighbor coupling.
Field-tuned quantum renormalization of spin dynamics in the honeycomb lattice Heisenberg antiferromagnet YbCl3
The basis for our understanding of quantum magnetism has been the study of elegantly simple model systems. However, even for the antiferromagnetic honeycomb lattice with isotropic spin interactions – one of the simplest model systems – a detailed understanding of quantum effects is still lacking. Here, using inelastic neutron scattering measurements of the honeycomb lattice material YbCl3, we elucidate how quantum effects renormalize ...
Strong phonon softening and avoided crossing in aliovalence-doped heavy-band thermoelectrics
Aliovalent doping is a way to optimize the electrical properties of semiconductors, but its impact on the phonon structure and propagation is seldom considered properly. Here we show that aliovalent doping can be much more effective in reducing the lattice thermal conductivity of thermoelectric semiconductors than the commonly employed isoelectronic alloying strategy. We demonstrate ...
Tuning magnetoelectricity in a mixed-anisotropy antiferromagnet
Control of magnetization and electric polarization is attractive in relation to tailoring materials for data storage and devices such as sensors or antennae. In magnetoelectric materials, these degrees of freedom are closely coupled, allowing polarization to be controlled by a magnetic field, and magnetization by an electric field, but the magnitude of the effect remains a challenge in the case of single-phase magnetoelectrics for applications.
Active learning-assisted neutron spectroscopy with log-Gaussian processes
Neutron scattering experiments at three-axes spectrometers (TAS) investigate magnetic and lattice excitations by measuring intensity distributions to understand the origins of materials properties. The high demand and limited availability of beam time for TAS experiments however raise the natural question whether we can improve their efficiency and make better use of the experimenter’s time.
Commissioning of the novel Continuous Angle Multi-energy Analysis spectrometer at the Paul Scherrer Institut
We report on the commissioning results of the cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle Multi-Energy Analysis) at the Swiss Spallation Neutron Source at the Paul Scherrer Institut, Switzerland. CAMEA is optimized for ...
Spin Density Wave versus Fractional Magnetization Plateau in a Triangular Antiferromagnet
We report an excellent realization of the highly nonclassical incommensurate spin-density wave (SDW) state in the quantum frustrated antiferromagnetic insulator Cs2CoBr4. In contrast to the well-known Ising spin chain case, here the SDW is stabilized by virtue of competing planar in-chain anisotropies and frustrated interchain exchange.
Dynamic magnetic crossover at the origin of the hidden-order in van der Waals antiferromagnet CrSBr
The van-der-Waals material CrSBr stands out as a promising two-dimensional magnet. Here, we report on its detailed magnetic and structural character- istics. We evidence that it undergoes a transition to an A-type anti- ferromagnetic state below TN ≈ 140 K with a pronounced two-dimensional character, preceded by ferromagnetic correlations within the monolayers. Furthermore, we unravel the low-temperature hidden-order within the long- range magnetically-ordered state. We find that it is associated to a slowing down of the magnetic fluctuations, accompanied by a continuous reorienta- tion of the internal field.
Dipolar spin-waves and tunable band gap at the Dirac points in the 2D magnet ErBr3
Topological magnon insulators constitute a growing field of research for their potential use as information carriers without heat dissipation. We report an experimental and theoretical study of the magnetic ground-state and excitations in the van der Waals two-dimensional honeycomb magnet ErBr3. We show that the magnetic properties of this compound are entirely governed by the dipolar interactions which generate a continuously degenerate non-collinear ground-state on the honeycomb lattice with spins confined in the plane.
Low-temperature magnetic crossover in the topological kagome magnet TbMn6Sn6
Magnetic topological phases of quantum matter are an emerging frontier in physics and materials science, of which kagome magnets appear as a highly promising platform. Here, we explore magnetic correlations in the recently identified topological kagome system TbMn6Sn6 using muon spin rotation, combined with local field analysis and neutron diffraction. Our studies identify an out-of-plane ferrimagnetic structure with slow magnetic fluctuations which exhibit a critical slowing down below T*C1 ≃ 120 K and finally freeze into static patches with ideal out-of-plane order below TC1 ≃ 20 K....
Waves on circular paths
Just as electrons flow through an electrical conductor, magnetic excitations can travel through certain materials. Such excitations, known in physics as "magnons" in analogy to the electron, could transport information much more easily than electrical conductors. An international research team has now made an important discovery on the way towards such components, which could be highly energy-efficient and considerably smaller.