Conveners
Oral Contributions
- Graeme Luke (McMaster University)
Oral Contributions
- Michael Graf (Boston College)
Oral Contributions
- Jun Sugiyama (CROSS Neutron Science and Technology Center)
Oral Contributions
- Peter Baker (ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory)
Oral Contributions
- Stephen Blundell (University of Oxford)
Oral Contributions
- Adrian Hillier (ISIS Neutron and Muon Facility)
Oral Contributions
- Hans-Henning Klauss (TU Dresden, Germany)
Oral Contributions
- Roberto De Renzi (Department of Physics and Earth Sciences, University of Parma, IT-43124 Parma, Italy)
Oral Contributions
- Khashayar Ghandi (University of Guelph)
Oral Contributions
- Tom Lancaster (Durham University)
Oral Contributions
- Sarah Dunsiger (TRIUMF / Simon Fraser University)
Oral Contributions
- Graeme Luke (McMaster University)
Oral Contributions
- Hubertus Luetkens (Paul Scherrer Institute)
Many magnetically frustrated systems exhibit what is known as persistent spin dynamics (PSD) in $\mu$SR experiments, the origin of which has remained mysterious since their discovery in the 1990s. As the temperature is lowered, the muon-spin relaxation rate rises (as would be expected for the slowing-down of spin fluctuations) but this rate then saturates at low temperature, the...
An important theme in magnetism is the understanding of phenomena in reduced dimensions using topology. Examples include excitations such as walls, vortices, merons and skyrmions, which exist in the spin textures of a range of systems [1]. Here we discuss case studies from our recent work, emphasising the ways in which muon site calculations, material simulation and $\mu$SR data can be...
Intrinsic magnetic topological insulators from the MnBi₂Te₄·(Bi₂Te₃)ₙ family have garnered significant attention as versatile platforms capable of hosting a range of exotic quantum states and phenomena, including higher-order topological phases, axion electrodynamics, and the quantum anomalous Hall effect. This tunability arises from manganese–pnictogen intermixing, which is sensitive to...
The metal-organic-framework compound Cu$_3$(HOTP)$_2$ is a small-gap semiconductor containing a kagome lattice of antiferromagnetically coupled $S$=1/2 Cu$^\mathrm{II}$ spins with intra-layer nearest-neighbour exchange coupling $J \sim $ 2 K. The intra-layer $J$ value obtained from calculations using density functional theory is shown to match with the experimental value for reasonable values...
Electronic correlations lead to heavy quasiparticles in three-dimensional metals, and their collapse can destabilize magnetic moments. It is an open question whether there is an analogous instability in one-dimensional systems, unanswered due to the lack of metallic spin chains. Recently, using neutron scattering, we reported a metallic correlated frustrated spin-1/2 chain compound, Ti4MnBi2...
Spin crossover (SCO) compounds are metal-ligand complexes which can easily switch their internal arrangement of electrons in d-orbitals from paired (low-spin) to unpaired (high-spin), by a minor variation in temperature, pressure, magnetic or electric field, or via irradiation. SCO is observed for some metal-organics containing Fe(II), Fe(III), Mn(III) or Co(II) ions, and the switching is...
Altermagnets are a novel type of magnetic system that has a spin-polarized electric band structure in the absence of a net magnetic moment. Microscopically this arises from two opposite spin sublattices that are connected by a lattice rotational symmetry instead of a simple translation or inversion [1]. A ferromagnetic-like transport response makes these systems particularly interesting for...
Establishing a sustainable society is one of the 21st century’s grand challenges. A key barrier is the efficient harvesting, storage, and use of clean energy. Addressing this requires developing new generations of functional materials and devices with advanced energy and quantum properties, which in turn demands control over matter at the nanometer, atomic, and subatomic scales.
In this...
Sodium ion batteries have been attractive and developed eagerly for practical use as one of post Lithium ion batteries. Battery materials NaCrO$_{2}$ and LiCrO$_2$ share an identical crystal structure: i.e., a two dimensional layered rock-salt type structure. NaCrO$_2$ shows high performance with a large capacity of 200 mAh in charge/discharge cycles, while LiCrO$_2$ has a small capacity in a...
To address carbon dioxide emissions, battery performance must be improved. Lithium-ion batteries (LIBs) dominate the market, but their limited and geographically concentrated resources have prompted research into sodium-ion batteries (NIB) to replace LIBs [1]. At J-PARC, we employed positive muon spin relaxation ($\mu^+$SR) [2] and small-angle neutron scattering (SANS) [3] in hard carbon,...
Palladium metal is known to be formed as palladium hydride PdH x by the penetration of dissociated hydrogen atoms into the crystal lattice in a hydrogen gas atmosphere, and has been studied extensively from the viewpoint of industrial applications as a hydrogen storage material. On the other hand, it is also known to exhibit superconductivity at high hydrogen concentrations at low...
At the U-line in J-PARC MLF MUSE, ultra-slow muons (USM) are generated by laser ionization of thermal muonium (Mu) in vacuum. Mu drifts in vacuum with a Maxwellian velocity distribution reflecting the production target temperature; consequently, the USM obtained from Mu ionization are also possess correspondingly low energies. At the U-line, a high-temperature tungsten target (2000 K,...
Muon microscopes [1-3] under development at J-PARC are reported. The transmission muon microscope (TμM) is an analog of a transmission electron microscope (TEM). By employing the strongest penetration power of muons into materials, the TμM allows us to visualizes the 3-dimensional distribution of electromagnetic field in objects much thicker compare to TEMs. This capability is useful to...
Muon Spin Relaxation measurements at continuous sources have stagnated at a stopped muons rate of 40 kHz and generally require sample sizes of at least 5 mm by 5 mm. Taking advantage of recent developments in pixel detector technology, we successfully implemented a prototype Si-pixel-based muon spin spectrometer at PSI. Unlike scintillator-based systems, this spectrometer utilizes the MuPix11...
Unconventional superconductors offer pathways to novel technologies and deeper insights into electron correlations in condensed matter. Noncentrosymmetric superconductors, lacking inversion symmetry, exhibit mixed spin singlet/triplet pairing, making them candidates for time-reversal symmetry (TRS) breaking in their superconducting states.
We have identified HfRhGe, a new noncentrosymmetric...
After three decades of research, the symmetry of the superconducting state in Sr2RuO4 is still under strong debate (1). The long time favoured spin-triplet px + i py state is ruled out by NMR experiments (2). However, in general time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two-component order parameters. Probing Sr2RuO4 under uniaxial pressure offers the...
We report the discovery of a remarkably rich phase diagram in the kagome superconductor YRu$_{3}$Si$_{2}$, uncovered through a unique combination of muon spin rotation, magnetotransport, X-ray diffraction, and density functional theory calculations. Our study reveals the emergence of a charge-ordered state with a propagation vector of (1/2, 0, 0), setting a record onset temperature of 800 K...
Bronze, an alloy mainly composed of copper with additions of tin and lead, has been used for creating historical cultural artifacts across the world. Analysis of the composition of these artifacts provides important insights into their manufacturing techniques, trade routes, and cultural backgrounds. However, surface degradation due to aging—such as oxidation, copper carbonate formation, and...
Muon-Induced X-ray Emission (MIXE) is a non-destructive analytical technique that combines the unique properties of negative muons with high resolution gamma detectors to perform depth-resolved elemental analysis. At PSI, the Germanium Array for Non-destructive Testing (GIANT) instrument leverages a high-intensity continuous muon beam (15–60 MeV/c) to implant muons at tunable depths (µm to cm...
A quantum spin liquid (QSL) is a long-sought magnetic state in which strong quantum fluctuations prevent magnetic ordering, allowing spin dynamics to persist at very low temperatures. Rare-earth triangular lattice compounds have proven to be a particularly promising platform to study spin liquid behaviours due to their localised f-orbitals and inherent geometric frustration. We present $\mu$SR...
Recently, bulk superconductivity has been observed in the layered nickelates La₃Ni₂O₇ and La₄Ni₃O₁₀ under hydrostatic pressure, with transition temperatures of up to 80 K. At ambient pressure, these compounds exhibit intertwined and non-trivial spin-density wave (SDW) and charge-density wave (CDW) orders.
In this work, we present a detailed investigation [1, 2] of the structural,...
The cuprate superconductor La2-xBaxCuO4 (x=0.125) is a striking example of intertwined electronic orders, where 3D superconductivity is anomalously suppressed, allowing spin and charge stripe order to develop, in a manner consistent with the emergence of a pair-density-wave state.
Understanding this interplay remains a key challenge, highlighting the necessity of external tuning for deeper...
Muon Knight shift measurements are a well-established method for determining pairing symmetries in superconductors, particularly effective for $f$-electron-based heavy fermion superconductors. However, precise measurements remain challenging in $d$-electron-based superconductors such as Sr$_2$RuO$_4$, where the Knight shift is intrinsically an order of magnitude smaller.
In this talk, we...
Superconductors that spontaneously break rotational symmetry in their electronic ground state are called nematic superconductors. Cu$_x$Bi$_2$Se$_3$ and CaSn$_3$ are two notable examples that have been studied extensively. Yet, proving the existence of the nematic superconducting state is challenging. Recent theoretical work predicts that odd-parity nematic SC should exhibit a unique magnetic...
Centrosymmetric GdRu$_2$Si$_2$ exhibits a variety of multi-$Q$ magnetic states as a function of temperature and applied magnetic field, including a square skyrmion-lattice phase. The material’s behaviour is strongly dependent on the direction of the applied field, with different phase diagrams resulting for fields applied parallel or perpendicular to the crystallographic $c$ axis. Using...
Multi-quantum (MQ) spectroscopy allows to selectively probe anisotropic muonium. The principal idea is to resonantly drive MQ spin transitions, for which both the electron and the muon spin flip simultaneously (Fig. 1a). In the high-field limit of the electron spin, such MQ microwave excitations are only possible in presence of hyperfine anisotropy, as demonstrated recently for bond-centered...
The remarkable thermal, optical and mechanical properties of beryllium oxide lead to a number of applications, however little is known about the behaviour of hydrogen in BeO, which can be as high as 4% in thin films. We used positive muons as a model for hydrogen. Earlier TF data [1] shows both diamagnetic and muonium states and a large "missing fraction".
We measured the muonium fraction...
The small amount of carbon in steel (<1%), critical in determining its properties, strongly depends on steel production technology. Destructive methods have been generally used to quantify carbon. Still, non-destructive and bulk analysis methods are required from the perspective of quality control in steel production and the analysis of cultural heritages. We propose a novel method of...
Radio-frequency muon spin resonance (RF-µSR) has been used to investigate the temperature dependence of the hyperfine parameters of the 2-Norbornyl radical formed in polycrystalline norbornene. Working at a fixed RF frequency of 170.5MHz, field scans show striking changes in both the resonance line shape and amplitude as the temperature is scanned through the plastic phase, with the signal...
The kagome lattice has attracted significant attention in the condensed matter community due to its rich sequence of emergent quantum phases, including chiral charge order, nematicity, superconductivity, and the anomalous Hall effect. Theoretical studies predict that these materials may host unconventional superconducting states, such as chiral superconductivity, making the experimental...
The mineral averievite Cu5V2O10(CsCl) possesses a different structure compared to herbertsmithite and other Cu-based kagome spin liquid candidates. The kagome layers are separated by two spacer layers, instead of one in herbertsmithite, reinforcing the 2D character.
The pristine averievite is known to order magnetically at 24 K due to Cu2+ magnetic interlayers but these can be replaced...
The antiferromagnetic semiconductor MnTe has recently attracted enormous research interest. Among other distinctions, MnTe has significance as a leading example of altermagnetism, a high-performance thermoelectric compound when lightly doped, and a platform for spintronics based on antiferromagnetic domains. Muon spin relaxation/rotation (µSR) studies of MnTe can help provide a more complete...
Hybrid systems combining superconductors (SCs) with magnetic atoms or molecules have revealed a rich landscape of emergent phenomena, including the formation of localized electronic states at their interfaces, with promising implications for spintronics [1]. In contrast to atomic impurities, magnetic molecules offer chemical tunability, enabling tailored coupling strengths between molecular...
The manipulation and observation of charge carrier distributions at the interfaces of semiconductor device structures is a fundamental problem in semiconductor physics. Standard electrical characterization techniques, such as deep level transient spectroscopy (DLTS) or capacitance-voltage (CV) measurements, have limited depth resolution and are unsuitable to probe the nanometer scale regions...
Metal-organic frameworks (MOFs) are composed of metal centres connected by organic polytopic ligands. Their high degree of chemical tunability is reflected in a controlled wide variability of the electronic states, among which magnetism. However, the main drawback against the realization of magnetic phases with high critical temperatures is the weak magnetic coupling between the metal centres...
The effect of pressure on an organic material is large due to its flexibility, and various physical states such as metal-insulator transition, spin liquid and superconductivity appear. Therefore, systematic research under pressure is important to understand their electronic or magnetic nature. The organic material, $\lambda$-(BEDSe-TTF)$_2$GaCl$_4$, is a Mott insulator and antiferromagnetic...
CsNiCrF$_6$ is a compound which exhibits multiple coulomb phases: charge ice, displacement ice and spin ice. Having all three of these Coulomb phases ensures that bulk techniques for measuring the dynamics in this compound struggle to grapple with the inherent disorder present [1], and density functional theory calculations on this compound are prohibitively expensive. In this talk, I will...
Critical phenomena at phase transitions in multiferroic materials remain not fully understood, and quantum beams drive the elucidation of the phenomena from the viewpoint of microscopic dynamical properties. BiFeO$_3$ is one of the most promising multiferroic materials with high antiferromagnetic ($T_N$$\sim$650 K) and ferroelectric ($T_C$$\sim$1100 K) transition temperatures [1]. We aim to...
Skyrmion lattices (SkLs) are intriguing vortex-like spin textures with non-trivial topology [1,2]. While they are typically stabilized by antisymmetric interactions in bulk noncentrosymmetric materials, centrosymmetric SkL hosts, such as Gd$_2$PdSi$_3$ [2–4], have recently been discovered. There, both the SkL stabilization mechanism under applied fields and the zero-field ground states (GSs)...
