The standard interpretation of the phase diagram of type-II superconductors was developed in the 1960s and has since been considered a well-established part of classical superconductivity. In particular, according to the standard picture, in a sample of type-II materials of a planar geometry in a parallel (in-plane) field, superconductivity nucleates at Hc3 approximately twice as big as the...
Ion transport in solids is a key feature for the operation of ion batteries. There are two parameters for describing ion transport in battery materials; one is a self-diffusion coefficient ($D^J$) and the other is a chemical diffusion coefficient ($D^C$). The former diffusion is caused by thermally activated fluctuation of ions, while the latter diffusion is caused by a flow due to a...
It is important to measure the temperature of the muon-production rotating target (hereinaf-ter referred to as "rotating target") in order to detect problems of rotating target quickly.
Thermocouples have been installed on the cooling jacket to measure the temperature rise due to thermal radiation from the rotating tar-get. Since the time constant of the thermocou-ples is on the order of...
How to choose analysis functions is a key matter to deduce the information in physics from the muSR results. For instance, local magnetic fields at the muon site in the paramagnetic state are well known to be coming from surrounding nuclear dipole moments. In this case, the field distribution at the muon site becomes to be the Gaussian distribution [1]. This Gaussian distribution typically...
The mother material of the La-based high-Tc superconducting oxides, La2CuO4(LCO), which family of materials possesses a d9 electronic configuration for copper ions, acts as a three-dimensional antiferromagnetic Mott insulator. LCO has been well investigated experimentally and theoretically in the past, but there are still questions on electromagnetic states to be...
We report muon spin rotation ($\mu$SR) studies of the superconducting properties as a function of chemical and hydrostatic pressure on the cubic ternary intermetallic (Ca$_{x}$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$ compounds, which feature strong coupling phonon-mediated BCS superconductivity and a structural phase transition a critical pressure p$_c$ associated with a charge density wave (CDW)...
The intermetallic compound MnSi exhibits a number of properties that have attracted strong interest. In particular it magnetically orders below 29.5 K to an exotic long-pitch helical structure. This type of order is due to the presence of the Dzyaloshinskii-Moriya interaction, authorized by the absence of inversion symmetry in the crystal structure, that coexists with a dominant ferromagnetic...
Bond-dependent interactions between magnetic moments can lead to strong frustration and nontrivial ground states. In particular, the Kitaev-Heisenberg model has a rich phase diagram and can host a spin liquid state or different frozen states depending on the strength of the additional Heisenberg interactions. Experimentally, such phase diagrams can be explored by modifying the relative...
We present a joint muSR and ab-initio study of the hydrogen impurity in magnesium oxide (MgO). Muon spin rotation measurements at magnetic high-fields reveal the presence of a diamagnetic configuration and of a muonium state, confirming an hyperfine interaction of 3.9(1) GHz at T=6K [1]. The temperature dependence of these states is followed up to room temperature, revealing a conversion of...
We have been developing a non-destructive, position-selective, and quantitative multi-elemental analysis method by using negative muons at J-PARC MUSE. Our final goal is to establish a platform of the integration of arts and science, where historical relics can be analyzed non-destructively, by combining quantum beams techniques utilizing muons, neutron or photons.
At the symposium, the...
[[Fig. 1 ($MnBi_2Te_4$) ($Bi_2Te_3$)n Zero Field μSR asymmetries vs. time at different temperatures][Fig1]
Time-reversal symmetry breaking in a topological insulator (TI) opens a surface gap and distinguishes chiral quantum states that could eventually be exploited in electrically controlled spintronic devices. The new approach to this state in a TI is with the intrinsic magnetic proximity of...
Metal hydrides have attracted attention as one of the candidate materials that can serve as safe and efficient hydrogen (H) storages. In particular, MgH$_2$ has great potential as a solid H-storage material because of its high storage capacity of 7.6 wt\%. However, its slow hydrogenation and dehydrogenation rates and the high decomposition temperature ($\sim$300$^\circ$C) are major obstacles...
A nano-size effect on magnetic materials shows novel and causes the magnetic properties different from those observed in a bulk form. The nano-size effect has been well investigated in metals but not yet explored in the high-Tc superconducting oxides. La2CuO4 (LCO) is a parental compound of La-based high-Tc superconducting cuprates which have a long-range...
$\mathrm{LiFePO}_4$ (LFPO) is an archetypical and well-known cathode material [1] for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure (see Figure) along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties [2]. At ambient pressure LFPO display an antiferromagnetic (AFM) spin order below $T_N = 53\;\mathrm{K}$ and neutron...
The fluorinated ionomer Nafion, first discovered by the DuPont company, is a material that provides efficient proton conducting membranes for application in important technological areas such as hydrogen fuel cells. Although many aspects of the polymer have been studied in relation to these applications, the microscopic mechanisms for proton transport in this polymer are still only poorly...
Ionic liquids (ILs) are a class of molten salts which are liquid at room temperature. Their properties are determined by strong electrostatic forces and generally include low volatility, negligible vapour pressure, and a low melting point. This makes them attractive candidates for improving battery and capacitor technology. The device effectiveness, however, is often determined by the ion...
Muon induced X-ray emission is a powerful technique for non-destructive elemental analysis for bulk material. This method have developed as practical quantitative analysis at J-PARC, and in present, this method have been applied for various samples, such as archeological artefacts, meteorite and so on.
In this paper, we report the results of applying this method to medical heritage in Japan....
A muonic atom is formed when a muon is captured in an atom system, and characteristic muonic X-ray emission occurs with the muon deexcitation process. The chemical composition of a material can be known based on the intensities of the emitted muonic X-rays. Non-destructive elemental analysis using negative muon beam has been highly developed in the last decade. This method provides a powerful...
In recent years, there have been increasing opportunities to consider about energy issues on a global scale, and the development of energy-saving technologies in various fields is highly desired. It is known that Fe-Cu-Nb-Si-B nanocrystalline alloy, so-called FINEMET(R), have higher magnetic flux density, higher linearity, and higher temperature stability than conventional materials....
The CaCu$_3$Ti$_{(4-x)}$Ru$_{(x)}$O$_{12}$ family, synthesized under high pressure (7.7 GPa) belongs to the perovskite class of materials. The ground state of the extremes of this solid solution are antiferromagnetic insulator for the x = 0 member, and itinerant-electron system, i.e., Pauli-paramagnetic metal, for the x = 4 member respectively [1,2]. The suppression of magnetic ordering...
In this presentation, I will show where positive muons shine light on nanochemistry uniquely, where they provide complementary information to pulse radiolysis and where the muon laser spectroscopy stand in this complementary world of positive muons and electrons. I will show some of our pulse radiolysis data and our muon spin spectroscopy data obtained from our work on different nanostructures...
A muonium is a purely leptonic bound system of a positive muon and an electron.
Fundamental properties of such a system can be precisely predicted by the QED, whereas ordinal atoms require to calculate hadronic interactions.
At J-PARC, the MuSEUM (Muonium Spectroscopy Experiment Using Microwave) collaboration aims to precisely measure the ground-state hyperfine splitting of muonium atoms,...
Using negative muon emission spectroscopy (µXES) can yield unique information by determining the composition beneath the surface whilst being completely non-destructive and has been shown to be a powerful technique for non-destructive analysis of the elemental composition of precious/rare samples. The characteristic muonic X-rays emitted after muon implantation can be used as fingerprints to...
Frustrated magnetism continues to be a vibrant area of research in chemistry and condensed matter physics. Geometric frustration arises when the magnetic degrees of freedom are incompatible with the underlying lattice geometry, and contrasts conventional magnetism because the system exhibits numerous degenerate ground states. Hence, rich exotic phenomena are observed as a function of pressure...
In an all solid state Li-ion battery, it is crucial to reduce ionic resistivity at the interface between the electrode and the electrolyte in order to enhance Li+ mobility across the interface, because Li$^+$ ions naturally drift across such interface. In particular, recent first principles calculations predict the presence of a space-charge layer (SCL) at the interface because of the...
Ultracold muonium (UCMu) is an important muonium (Mu) source for the generation of ultraslow muon beam [1-3] for nanotechnological applications and understanding hydrogen dynamics in materials. In order to search a new solid material for the generation of UCMu in vacuum, we have studied n-Si [4], SiC and KCl at low temperatures (5 K – 300 K) using conventional $\mu$SR method. The relaxation...
The hole-doped organic superconductor $\kappa$-(ET)$_{4}$Hg$_{3-\delta}$Br$_{8}$, ($\kappa$-HgBr), where $\delta$=11% and
ET=bis(ethylenedithio)tetrathiafulvalene, has been the key to bridge the knowledge gap between half-filled organics and doped cuprate systems. Nonetheless, the isotropic triangular lattice of ET dimers of $\kappa$-HgBr, unlike the square lattice in cuprates, is suspected...
Understanding the complex ways that battery materials change on charging and discharging is vital for improving their function in operation, but traditional ex-situ muon measurements have barely scratched the surface of this deep mine of information. Here, we present an electrochemical cell that enables ionic diffusion measurements using muon spectroscopy (μSR) at the ISIS Neutron and Muon...
The recently reported electrochemical sugar recognition system consisting of a nano-sized gold particle (GNP) with a diameter of 10 nm, a ruthenium complex and a pheylboronic acid, attracts much interest because of its high sensitivity for various sugars such as D-glucose or D-fructose. When sugar molecules are attached to the phenylboronic site, the response of electrochemical voltammetry of...
We present high magnetic field $\beta$NMR measurements of $^8$Li$^+$ implanted in single crystals of sapphire, a commonly used backing material for other samples. From the well-resolved quadrupolar splitting, we extract the electric field gradient (EFG) at the implanted $^8$Li$^+$ site. Comparison with supercell density functional theory calculations of the EFG allows us to identify the...
This paper reports the development of a novel technique using spin polarised positive muons to probe local charge redistributions within polymeric dielectrics under externally applied E-fields (EEF’s). These materials are used in many high voltage applications, and knowledge of charge dynamics is crucial to their successful use, as it dictates their ultimate ability to function as a...
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. Recently, we explored magnetic correlations in the kagome magnet Co$_{3}$Sn$_{2}$S$_{2}$ [1]. Using muon spin-rotation (${\mu}$SR) and ARPES, we present evidence for competing magnetic orders in the...
The convergence of two major research strands in modern condensed-matter physics: topological materials and unconventional superconductivity, constitutes a new field of study. Topological materials with Kramers or hourglass fermions represent a special subclass, recently realized in materials lacking inversion symmetry or with a nonsymmorphic space group. At the same time, there is a surge of...
The analysis of depth-dependent data of thin-film film semiconductor heterostructures is discussed in this work. The data is obtained by varying muon implantation energy, E, using the Low Energy Muon facility (LEM) at PSI, Switzerland. Since the measurement method has a finite resolution, deconvolution of the measured profile with the resolution function is required. The unfolding can be...
Cuprate high-temperature superconductors have complex phase diagrams with multiple competing ordered phases. Understanding to which degree charge, spin, and superconducting orders compete or coexist is paramount for elucidating the microscopic pairing mechanism in the cuprate HTSs. In this talk, I will report some novel results of muon-spin rotation (µSR) and AC susceptibility experiments on...
The observation that the glass transition temperature of polystyrene (PS) thin films decreases with decreasing film thickness led to the suggestion that there is a very thin layer near the free surface where the polymer motion is faster than in the bulk. Direct confirmation of enhanced dynamics near the free surface has proved elusive as few techniques can measure how the dynamics varies with...
Glasses occupy more volume than required for molecular close packing. The distribution of this ``free volume'' is related to other key properties such as dynamic heterogeneity (stretched exponential relaxation). As a glass ages, it equilibrates by thermally activated structural relaxation producing permanent densification with slowed relaxation times. Mechanical deformation can significantly...
Time-reversal symmetry breaking is a signature of unconventional superconductivity and can be observed from zero-field muon spin relaxation measurements as an increase of the muon relaxation rate through the superconducting transition temperature. Time-reversal symmetry breaking, although rare, has been observed in several noncentrosymmetric rhenium-based intermetallic superconductors...
The Super-Omega beamline at J-PARC Materials and Life Science Experimental Facility provides an intense pulsed surface muon beam. Combined with a muonium production target and a laser for muonium ionization, the pulsed ultra-slow muon facility has been developed. At the facility, a spectrometer for the muon spin rotation measurements using the ultra-slow muons is under commissioning. In this...
Quantum spin liquids (QSLs) represent a state of matter governed by long-range quantum entanglement. These states are stabilized by geometric frustration and remain magnetically disordered even at zero temperature. Of particular interest, are the new exotic fractional excitations with S = ½, so-called spinons. Kagome antiferromagnets are known as one of the most promising systems for the...
We present an updated model for muonium properties and behavior in silicon carbide (polytype 6H; SiC) based on new (unpublished) and published results from our group’s TF-, LF-, RF- and photoexcited MuSR measurements.
SiC is known and widely used for structural ceramics due to its physical properties (e.g. high thermal conductivity; hardness; strength; resistance to corrosion and abrasion)...
Cadmium oxide is a transparent conducting oxide (TCO) that has many applications in optoelectronic devices, such as solar cells, photo transistors and diodes. CdO is a naturally n-type TCO with hydrogen acting as a shallow donor. MuSR zero field measurements were collected, from 20 K to 800 K, to investigate the diffusion properties of positive Mu defects in a CdO powder sample. The neutral Mu...
Tin oxide is a transparent conducting oxide (TCO) that has many applications in optoelectronic devices, such as solar cells and LED’s. Tin oxide is naturally n-type with hydrogen acting as a shallow donor. MuSR zero-field measurements were taken on a single crystal sample from 2 K to 710 K in a closed cycle refrigerator and from 300 K to 1080 K in an optical furnace. The zero-field...
The analysis of muon spin relaxation experiments typically relies on model fitting under conditions that are ill-posed. Typically models are selected to fit the data based on the inductive bias (physical intuition) of the experimentalist. Although recent studies have demonstrated the application of unsupervised machine learning to automatically detect model changes...
When a negatively charged muon stops in a material, the muon makes muon atomic orbitals around an atomic nucleus in the material. The muon orbiting its 1s orbital is absorbed into the nucleus with a mean lifetime depending on the atomic number of the nucleus (Z). This no-electron-emission process competes with the natural decay of the muon into an electron with a lifetime of 2.2 μs. The...
Reduction of the momentum width in the muon beam is required in particle physics and material science. A small-momentum-width muon beam so called ultra-slow muon beam can be realized by laser ionization of muonium which can be produced by stopping of surface muons in a solid target and thermally diffusing them. Such an ultra-slow muon generation technique reduces the momentum width to about...
Spin lattice relaxation is the simplest type of $\beta$NMR measurement. The usual approach is to implant a pulse of hyperpolarized nuclei and monitor the time-resolved $\beta$-decay asymmetry, yielding the ensemble average spin-lattice relaxation. In the simplest case, the asymmetry decays exponentially with a characteristic time constant $T_1$, but this ideal is rarely obtained in practice....
Silicon carbide (4H-SiC) is a wide-bandgap semiconductor with applications in high power devices. Epitaxial growth of SiC is crucial to produce structures with controlled thickness and doping concentration. Ion implantation with nitrogen (N) and phosphorus (P), on the other hand, is used to create spatially defined n-type regions in SiC. Implantation is usually followed by a post-implantation...
The Meissner state (MS) is the state with the most pronounced superconducting properties. Therefore, knowledge and understanding properties of the MS is a necessary condition to understand and predict properties of all other states of all superconductors. The standard interpretation of the MS is based on the theory of F. and H. London, with minor modifications adopted in the Ginzburg-Landau...
Gallium oxide $\beta$-Ga$_2$O$_3$ is currently drawing much attention as a material for high-voltage power devices because of its large band gap ($E_\mathrm{g}\sim$4.9 eV). We investigated the electronic structures of muon as a pseudo-hydrogen in $\beta$-Ga$_2$O$_3$ in which the dilute hydrogen is under the central focus as a crucial factor for the bulk conducting properties. We demonstrate by...
Fe4Si2Sn7O16 displays an undistorted kagome lattice of Fe2+ (3d6, S = 2) ions. We present results of DC-pulse-field magnetisation up to 50 T, Nuclear Magnetic Resonance (NMR), AC-susceptibility and muon-spin-resonance (µSR) measurements down to 19 mK on powder sample of Fe4Si2Sn7O16. The magnetization measurement at 2 K excludes the presence of strong Ising anisotropies. In the temperature...
Electronic correlations play a key role in tuning the properties of parent- and doped (superconducting) iron pnictides, ultimately determining their respective ground states. Parent compounds with magnetic doping are particularly intriguing, since dopant coupling via Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions depends significantly on the strength of electronic correlations, which...
Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of Cooper pairs, leading to zero resistivity and diamagnetism.
Here we report a set of thermodynamic, transport and muon spectroscopy observations on a series of hole-doped Ba$_{1−x}$K$_x$Fe$_2$As$_2$. Our specific-heat measurements...
The arrangement of magnetic moments at the vertices of a pyrochlore lattice - composed of corner-sharing tetrahedra - leads to a great variety of electronic ground states for $R_{2}M_{2}$O$_{7}$ materials. Here, we present an in-depth analysis of muon-spin spectroscopy measurements of Eu$_{2}$Ir$_{2}$O$_{7}$ under the effect of the Eu$_{1–x}$Bi$_{x}$ isovalent and diamagnetic substitution [1]...
Theoretical study using density functional theory (DFT) calculations supports to estimate the stopping site of muon in materials and understand the muon spin rotation and relaxation ($\mu$SR) measurements. To understand the temperature dependent zero-field (ZF) $\mu$SR measurement in water, we have performed DFT calculations and quantum simulation to estimate the muon sites in hexagonal (Ih)...
Na$_2$Ni$_2$TeO$_6$ honeycomb layered oxide has suitable properties for use as a Na-ion battery cathode material. The substitution of Ni with Co has been shown to have a detrimental effect on the energy density of Na$_2$Ni$_2$$_-$$_x$Co$_x$TeO$_6$, whereas the plateau potential vs Na$^+$/Na increases. Thus, to ascertain the cause of the electrochemical properties change upon substituting Ni...
$\mu^+$SR is used in various research fields as a sensitive local magnetic probe. Although the implanted $\mu^+$ stop at interstitial sites in the crystal, it is often difficult to determine the sites precisely. On the other hand, the implanted $\mu^-$ are captured by nuclei and have different lifetimes for each nuclide. Thus, the $\mu^-$ position is unambiguously determined by measuring the...
During the $\mu^-$SR measurements on Li-ion battery materials, a part of implanted $\mu^-$ is naturally captured by Li nucleus, leading to the formation of muonic-Li species in target materials. The past $\mu^-$SR study on Li metal shows the lack of relaxation in the TF-$\mu^-$SR spectrum at room temperature [1], despite the presence of large nuclear magnetic fields at the muonic-Li position...
In our efforts to help the earth recover from ecological burnout we have been trying to bridle the sun’s energy since 1954, when the first practical silicon solar cell was introduced. Today we are researching for ever higher efficiencies, while we try to make use of earth-abundant materials. Perovskite solar cells are promising candidates for next generation photovoltaic technology due to...
J-PARC MUSE is responsible for the inter-university user program and the operation, maintenance, and construction of the muon beamlines, namely D-line, S-line, U-line, and H-line, along with the muon source at MLF.
At D-line, which provides the world’s most intense pulsed negative and positive muon beams, various scientific studies, including those on industrial applications, archeology, and...
The surface muon beamline (S-Line) in the experimental hall No.1 of the Materials and Life science experimental Facility (MLF), J-PARC is designed to provide low-energy muon beam, which is mainly utilized by materials and life science experiments. The final goal of S-Line is a beamline with four experimental areas from S1 to S4, of which the first experimental area S1 started in 2017 for user...
This work describes the new M9H muon decay channel at TRIUMF, which is specifically designed to deliver high quality transversely spin polarized beams. Transverse polarizations in both X and Y of ~80% over the momentum range 70-120MeV/c are expected. In contrast to a traditional z-polarized decay beam the key to accomplishing this task lies in the extraction an off-centre momentum-canted...
Ga$_2$O$_3$ is an emerging wide-gap semiconductor with a broad variety of applications, from transparent conduction to high voltage applications, therefore considered as a possible replacement for SiC. Its alpha polymorph, which can be grown in bulk crystalline form, is intensely investigated. An important technological development relies on the growth of thin film of the epsilon polymorph,...
The low energy $\mu$SR (LE-$\mu$SR) spectroscopy is primarily used to study thin films, surfaces, and interfaces of materials. However, because of the large beam spot and low implanted muons rate, LE-$\mu$SR measurements on small samples are difficult, requiring an optimal sample area of $ 25\times25$ mm$^2$. Recently, we have boosted our ability to measure small samples, down to $5 \times 5$...
The D-line of the J-PARC MLF MUSE has a pion decay section, which makes it possible to use decay muons. The superconducting solenoid magnet used in the pion decay section has a large bore and thus produce the world's highest positive and negative muon intensities. Since the D-line is currently the only beamline at MUSE where practical negative muon intensity is available, various user...
In the late 1970s and 1980s $\mu^+$spin rotation experiments were performed elaborately to study $\mu^+$ diffusion and trapping in Fe and Fe alloys. In Fe alloys not many experiments were performed, probably because the unavoidable inhomogeneity of the magnetization in ferromagnetic Fe alloys bring about the fast dephasing of spin rotation and may obscure the diffusion and trapping effects....
Super-MuSR is a major project to upgrade the MuSR instrument at ISIS that aims to provide an order of magnitude increase in resolution and counting rate in separate modes of operation. This now forms an early part of the ISIS-wide Endeavour programme, an estimated £90m investment in new and upgraded instruments, which we are aiming to start in the 23/24 financial year.
Experiments using...
One of the key challenges in the condensed matter research field is understanding the pairing mechanisms that give rise to unconventional superconductivity. Transition metal dichalcogenides $MX_2$ ($M$ = Nb, Ti, Ta, Mo and $X$ = S, Se) are a class of materials that have been shown to exhibit competition between a charge density wave (CDW) and superconducting state [ 1]. In ambient conditions,...
A positively charged muon implanted in copper sits at an octahedral interstitial site and experiences a magnetic dipolar coupling with six nearest-neighbour quadrupolar $I=3/2$ copper nuclei [1]. The resulting avoided level crossing resonance observed as a function of magnetic field [2] provides a means of studying these interactions and understanding the effect of the electric-field gradient...
Various $\mu^+$SR techniques have been widely used for studying internal magnetic fields in assorted materials [1], such as, antiferromagnets, spin-glasses, paramagnets, and superconductors. However, for ferromagnetic (FM) materials, $\mu^+$SR faces a difficulty in determining the correct dipole field at the muon site $({\bf H}_{\rm dip})$ because the internal magnetic field at the muon site...
The very first low-energy muon spin rotation (LE-$\mu^+$SR) study performed on LiTi$_2$O$_4$ films in the Meissner state is presented. LiTi$_2$O$_4$ is a unique spinel type superconductor in which the mechanism underlying superconductivity is highly debated [1]. LE-$\mu^+$SR is a direct probe for the characterization of depth dependent properties in thin films, which allowed us to extract...
This poster presents an overview of the software tools and techniques that have been developed as part of the Muon Spectroscopy Computational Project (MSCP). The MSCP is an initiative that currently includes: (a) the Muon Group at ISIS; (b) the Scientific Computing Department; (c) the UK Software Sustainably Institute and (d) Members of the [Galaxy][1] platform. The main objective of the...
Here, we report on the status of the setup, commissioning and first performance tests of the newest muSR instrument FLAME (FLexible and Advanced MuSR Environment) at PSI. Commissioning started in spring 2022 after the delivery of the superconducting experimental magnet.
FLAME is designed to allow ZF, LF and TF muSR measurements over a broad temperature range from 25mK to 300K with magnetic...
At J-PARC MLF, MUSE provides the world-highest flux of pulsed muon beams. U-Line, one of the four beamlines in the facility, features an intense surface muon beam from Super-Omega and Ultra-Slow Muon (USM) generated by laser ionization of thermal muonium in a vacuum. The beamline has two branches: U1A for muon spin spectroscopy using USMs and U1B for transmission muon microscope. The unique...
We have designed and constructed a thin film preparation chamber with base pressure of $<2 \times 10^{-9}$ mbar. Currently, the chamber (see figure) is equipped with two large area evaporators (a molecular evaporator and an e-beam evaporator), an ion sputtering gun, a thickness monitor and a substrate heater. It is designed such that it can handle large area thin film samples with a future...
We present a theoretical calculation for feasibility study of the Muon Microscope, which is intended to add positional resolutions within the sample by tracking down the positron trajectories to its source positions. In the presence of a magnetic field, any positrons whose trajectories have components which are perpendicular to the magnetic field will start to move in a helical path due to the...
Avoided level crossing muon spin resonance (ALC-$\mu$SR) has been used to study the dynamics of the alkyl chains and cholesterol within model biomembranes composed of phospholipids (DPPC and POPC) and cholesterol. ALC-$\mu$SR is sensitive to motions on timescales between that measurable by NMR and neutron scattering. Muonium adds to the unsaturated C=C bonds of POPC and cholesterol to give in...
The inverse perovskite Sr$_3$SnO is a 3D cubic Dirac semimetal with a very small energy gap, a so-called topological crystalline insulator$^1$. The unusual electronic structure confers a variety of novel properties, such as chiral topological surface states, and very strong itinerant electron orbital magnetism. Remarkably, when doped it also becomes superconducting$^2$. In the most insulating...
Using muon-spin rotation (μSR) [1] the magnetic fields of Fe3O4 have been previously investigated. The Verwey transition at Tv (~123 K) and a transition at Tw (~247 K) are observed. Using Maximum-Entropy (MaxEnt) μSR data of single-crystal Fe3O4 are analyzed with much improved precision. [2,3] We review earlier results [3] and report on our analysis of the temperature dependence of fields...
CeO2 is a material that has been widely used in industrial fields such as catalysts and sensors. It is believed that oxygen deficiencies and hydrogen at the deficient positions play an important role in these functions, but the details, including the electronic state, have not been clarified. It has been reported that muons implanted in CeO2 are bound to electrons and form muonium [S.F.J.Cox...
The Fe-based superconductors have been extensively investigated in view of the intimate interplay of the magnetic and superconducting phases developing therein. Here, we show an anomalous behaviour of the mixed phase in the family of superconducting compounds LaFeAsO$_{1-x}$F$_{x}$ as detected by transverse-field muon spin rotation. This technique is the best tool to probe both the flux line...
To support the continued growth of μSR, it is important to encourage prospective new users by minimizing any barriers to entry to the μSR community. As with any other scientific approach, one such barrier to entry can be the software tools necessary to extract useful information from the data. Although excellent software options for μSR currently exist, in our experience, students and other...
Cross-polarization techniques provide a rich playground which allows NMR practitioners a large variety of tools to extract detailed spin-hamiltonian parameters of inhomogeneous systems. Beta-detected NMR is almost an ideal arena, i.e. one spin-polarized 8Li residing in a local structure, for which to apply such multi-resonant pulse sequences.
As such, an adaptation of NMR's BRAIN-CP RF...
In the past years, in the framework of a successful collaboration between RIKEN-RAL and INFN, (CHNET-TANDEM collaboration) a series of experiments were carried out to optimize Muonic Atoms X-rays Spectroscopy as a non-invasive and non-destructive probe for quantitative elemental characterization of ancient metal artefacts of particular interest. We present the results on late Bronze-age...
One famous model for a two-dimensional magnetic system is the Shastry-Sutherland (SS) model, which considers an orthogonal dimer network of spin S = 1/2 [1]. The model predicts a dimer ground state for J/J’ < 0.5, and a 2D antiferromagnetic (AFM) phase with significant quantum fluctuations is expected for J/J’ > 1 [2]. However, the ground state of the intermediate region (0.5 < J/J’ < 1) has...
The study of thin-film and multi-layered structures with nanometer resolution is possible with low energy $\mu$SR (LE-$\mu$SR). The average stopping depth of the positive muons with implanted energies between 1 and 25 keV extends over a few nanometers and depends on the density of the probed material.
Modeling of the measured $\mu$SR parameters such as diamagnetic asymmetry and relaxation...
The first principle calculation involving muon needs to consider the effect of quantum fluctuations as well and it is still in a state of development. In order to verify the first principle calculation, the basic data for the collision cross section at low energy region corresponding to the binding energy of the muon and the target molecule is necessary. Especially the elastic scattering cross...
The development of the next generation ‘Super-MuSR’ instrument at ISIS will provide a transformational improvement in counting rate (to 1000M ev/hr) and timing resolution (to better than 2ns) for pulsed beam measurements. Key to delivering this capability is the highly pixelated cylindrical detector array, built as 64 long ‘barrel staves’. This totals 704 pixels providing 75% solid angle...
We have recently begun an investigation of paramagnetic (free-radical) final states formed on metal nanoparticles by muonium reactivity with surface-adsorbed molecules. The nanoparticles are incorporated into mesoporous silica, facilitating specific reaction steps in the silica host that involve H-atom transfer reactions important to studies in heterogeneous catalysis. Radio-frequency (RF)...
To obtain one time-differential $\mu$SR spectrum using a conventional technique, we must wait around $10^2$ minutes. In the majority of $\mu$SR experiments, the $\mu$SR spectrum is recorded as a function of temperature. Thus, such a long recording time ($t_{record}$) has not been a serious problem, because the lead time ($t_{read}$) for stabilizing temperature requires typically 10-20 min,...
Ultra-slow negative muon production is under development in J-PARC.
It may explore new fields in material science, such as surface science, precise depth analysis of sample materials after re-acceleration, and 2 or 3 dimensional scanning of samples after re-acceleration and focusing. It may also contribute to explore new fields in Particle physics. Production of both the negative and positive...
Copper based busts in the shape of heads or shoulder high length, are known from the Renaissance, e. g. the small statuettes of the Virgin and Christ, with heights under 15cm by François Duquesnoy [1] to busts of heights over half a meter [2]. The bust presented in this paper has no comparison to Renaissance statuettes. The contorted face of the Bust, height about 22cm, reminds one of the...
Materials showing high photoresponsive electrical resistance have attracted considerable attention due to their photoelectronic applications.[1] Recently, we have reported that yttrium oxyhydride (YO$_x$H$_y$) epitaxial thin films exhibit a repeatable photo-induced insulator-to-metal transition by UV laser illumination and thermal relaxation.[2] The photo-induced metallization likely...
Tuning the energy of incoming muons in the low energy muons (LEM) spectrometer is done primarily by applying a high voltage (HV) on the sample plate to accelerate or decelerate the implanted muons. Therefore, any manipulation on the sample that requires the use of direct contacts to it becomes complicated. For example, in order to run a current through the sample or apply an electric field on...
The muon and muonium play a unique role in materials science as a tiny magnetometer and an emulator of hydrogen in matter. However, there are few examples of their application as matter waves. This is because the surface muon and its simple slowing-down in a degrader cannot keep sufficient coherence. Low-energy muons from laser ionization of muonium can be used to obtain slow muonium with...
After the first observation of magnetic skyrmion in 2009, the so-called skyrmionics research field is still rapidly evolving. To this day, intense research effort is still carrying on in understanding their intrinsic properties for the potential realization of future energy efficient nanodevices. Magnetic skyrmion in thin multilayer films are appealing because their emergence, stability, and...
Lithium-ion (Li-ion) batteries are commonly used as energy storage device for both mobile and stationary applications. Even though the Li-ion technology is clearly a huge success story for modern electrochemistry, lately, there has been serious concerns regarding several aspects, e.g., availability and price of lithium raw material [1]. Consequently, the industry is currently and actively...
KAgF$_3$ is an antiferromagnet, consisting of Ag ions in the rare 2+ oxidation state which magnetically order at low temperature [1, 2]. Here we present a detailed $\mu$SR study of the compound, showing how measuring high statistics data in the high temperature, non-magnetic phase can be used to obtain information about the muon site. Knowledge of the muon site then guides the analysis of the...
As known (Landau, 1937), the equilibrium domain structure of the magnetic flux in type-I superconductors in the intermediate state is formed due to the competition between the energy contributions to the sample free energy arising from the superconducting/normal interfaces, on one side, and the contributions due to an inhomogeneous field distribution and the domains shape (FDDS) near the...
In the context of $\mu$SR studies on magnetic materials in the ordered state, often a strong initial depolarization is found in the zero field spectra. For transverse field measurements this is often referred to as a loss in asymmetry. In case of the low-energy muSR (LE-$\mu$SR) setup this needs a more detailed discussion since effects such as time-of-flight distribution decay, back...
In intermetallic Ce- and Yb-compounds, the hybridization between the 4$f$ and itinerant conduction electrons induces the magnetic instability and charge configurations, and the ground state properties of heavy fermion located in the vicinity of a magnetic quantum critical point (QCP) is one of important issue for strongly correlated electron systems. The cubic compound YbCo$_2$Zn$_{20}$ has...
Ruthenium dioxide RuO$_2$ is a well-known catalyst applied in various fields due to its high electrical conductivity and chemical stability. Although rutile RuO$_2$ has long been regarded as a Pauli paramagnetic metal, recent neutron diffraction experiments and resonant X-ray scattering have suggested the presence of an antiferromagnetic order ($T_\mathrm{N}>300~$K: Ru moment size...
Rhenium oxide compounds of the type AReO$_4$ where A is a first-row transition metal cation, exhibit interesting electronic properties. Among this family of compounds, MnReO$_4$ was the first of this kind, synthesized with a high-pressure technique at 25 kbar in 1970 [1]. It has a wolframite structure where both cations have partially filled d shells, and an anisotropic electrical...
We present muon spin spectroscopy ($\mu$SR) measurements on the antiferromagnetic Mott insulator NiS$_2$. This compound features two subsequent magnetic phase transitions around 38.9K and 29K associated with the opening of a Mott gap. From the the rotation dependence of transverse field $\mu$SR measurements (Fig. 1b) we confirm the magnetic space group 205.33 in the 38.9K to 29K phase, refined...
Elemental palladium (Pd) is a well-known paramagnetic transition metal. Doping with iron impurities leads to giant magnetic moment formation and spin glass behavior. Pd surfaces often show different behavior than bulk Pd [1,2], which is particularly relevant in research fields working with Pd nanomaterial, such as for example catalysis and spintronics.
We present depth-dependent transversal...
In Mott insulators, band electrons are localized due to strong electron-electron interactions. Although the s-electrons of alkali metals are very delocalized, by confining them in the periodic nanospace of zeolite crystals and making them moderately localized, such a strongly correlated electron system can be created.$^1$ In sodalite, $\beta$-cages with an inner diameter of 0.7 nm are arranged...
We present the results of a muon-spin relaxation ($\mu^{+}$SR) investigation of the crystalline organic radical compound 4-(2-benzimidazolyl)-1,2,3,5-dithiadiazolyl (HbimDTDA), in which we demonstrate the hysteretic magnetic switching of the system that takes place at $T = (249 \pm 13)\,\mathrm{K}$ caused by a structural phase transition. Muon-site analysis using electronic structure...
Our purpose is precision measurement of the 1S-2S energy interval in Muonium, which is an exotic hydrogen-like atom consists of a positive muon and an electron. This purely leptonic system enables a precise calculation of the energy interval with the Standard Model without any concerns of the uncertainty from the charge radius of the nucleus, unlike the hydrogenatom. This advantage motivates...
Although $\mu^+$SR is widely used as a tool for studying a microscopic internal magnetic field in condensed matters over 40 years, the counterpart technique, i.e., $\mu^-$SR is less common for such purpose mainly due to a low counting rate for reaching reliable statistics. However, the recent progress in the beam power and counting system overcame such problem. We therefore started a new...
Online learning is being adopted across a wide range of disciplines as remote access to resources, widening participation in training, and an appreciation of the diverse approaches of learners have come to prominence. Online resources can also be used to augment more traditional in-person training by bringing a cohort of learners up to a common minimum level beforehand, distributing materials...
In recent years, 5d transition metal oxides have been the focus of increasing research interest, owing to their rich physics emerging from the interplay between electron correlations and strong spin-orbit coupling (SOC). Such SOC-induced insulating phases are frequently accompanied by the transition of the 5d ion to a magnetic state triggered by local structural distortions, in competition...
We present a piezoelectric-driven uniaxial pressure cell operable at cryogenic temperatures and optimized for muon spin relaxation and neutron scattering experiments. These methods often require larger sample sizes, and so the cell is designed to generate a force of up to ~ 1000 N. It incorporates calibrated displacement and force sensors, the combined knowledge of which can determine quickly...
LaAlO$_3$ is a wide bandgap, transparent oxide commonly used as a substrate for epitaxial film growth and as a vacuum-like electrically insulating layer in heterostructures. Below a soft-mode structural phase transition at about 800 K, it is rhombohedrally distorted from the ideal cubic perovskite structure as the AlO$_6$ octahedra rotate about the cubic $\langle 111 \rangle$ directions$^1$....
Artificial spin ices, which are composed of dipolar coupled arrays of elongated nanomagnets, host a broad range of physical phenomena usually the preserve of bulk condensed matter[1]. In particular, collective phase transitions between ordered and disordered states have been well documented in these nanomagnetic systems[2]. The complex phases observed in artificial spin ices occur as a...
The recent surge of Li-ion batteries has triggered an increased interest to investigate Na-ion battery materials [1,2], because Na is more abundant than Li, resulting in lower material costs. Although many Na transition metal oxides are available as a cathode material for the Na-ion battery, there is, at present, no suitable anode material [1]. The most common anode materials for the Li-ion...
Muoniated vinyl radicals can be produced by Mu addition to triple bonds. Rhodes et al. observed a muoniated radical formed by Mu addition to trimethylsilylacetylene but were unable to determine the structure.1 We have performed additional transverse field muon spin rotation measurements on trimethylsilylacetylene at 298 K and observed that two muoniated radicals were formed; a major...
Muon probing hydrogen study is based on the fact that the target material contains at least a small amount of hydrogen. Therefore, a high-sensitivity measurement of hydrogen abundance would be useful as a complementary measurement of $\mu$SR experiments. We are developing a high-sensitivity thermal desorption spectrometry (TDS) system to perform such complementary measurements.
TDS is known...
We report progress of which examines the thermal stability of the muon production target up to high temperature regime. We employed the high-frequency induction heating system as an indirect heater to target material, graphite, used with various purposes such as kitchenware, small blacksmiths. Prior to applying muon production target, we tested simple disc graphite with small chamber and RF...
For quantum systems/materials, a standard procedure for probing this behaviour is to try to tune these properties using external parameters to put the different phases of the material onto a phase diagram. Pressure application is a widely used tool to tune these properties, using a given pressure cell device. This can be a problem when using Muon Spin Rotation/Relaxation (µ+SR) as a large...
In calculations supporting μSR, it is important to deal with muon quantum effects. In previous studies, people have gone beyond the point-like muon approximation by using methods such as vibrational analysis of the zero point motion and path-integral molecular dynamics.[1-3] We now use a new method called Two-component DFT (TCDFT), which treats the muon as a fully quantized particle with its...
We report the surface muon beamline design of the Muon station for sciEnce, technoLOgy and inDustrY (MELODY) project based on China Spallation Neutron Source (CSNS). Based on the 1.6GeV proton beam, a surface muon beam line has been designed to deliver a muon flux of 10^5μ+/s to the μSR experiment area. In order to transport the large emittance muon beam, a series of solenoids for focusing...
The Phase II upgrade project of the China Spallation Neutron Source includes the construction of a surface μ beam line and a μSR spectrometer, which will be the first μSR spectrometer built in China. Here we report the conceptual design of the spectrometer including the sample environment. Based on the design parameters of the muon beam, we design the spectrometer with a large number of...
The search of quantum spin liquid (QSL), an exotic magnetic state with strongly-fluctuating and highly-entangled spins down to zero temperature, is a main theme in current condensed matter physics. However, there is no smoking-gun evidence for deconfined spinons in any QSL candidate so far. The disorders and competing exchange interactions may prevent the formation of an ideal QSL state on...
A Muon station for sciEnce, technoLOgy and inDustrY (MELODY) project will be constructed at China Spallation Neutron Source. The Phase I project will provide a surface muon beam with a pulse width of 100 ns at a rate over 10^5 µ+/pulse. Accurate monitoring of the muon beam intensity is essential for the calibration of the µSR spectrometer. The key of the beam intensity measurement is to...
Quantum fluctuations are expected to lead to highly entangled spin-liquid states in certain two-dimensional spin-1/2 compounds. We have synthesized and measured thermodynamic properties and muon spin relaxation rates in the copper-based two-dimensional triangular-lattice spin liquids Lu$_3$Cu$_2$Sb$_3$O$_{14}$ and Lu$_3$CuZnSb$_3$O$_{14}$. The former is the least disordered of this kind...
The accelerator complex of China Spallation Neutron Source (CSNS) is delivering a proton beam of 100 kW in beam power, 1.6 GeV in kinetic energy and 25 Hz in repetition rate, which will be upgraded to 500 kW in the CSNS-II project. A muon facility, the so-called Experimental Muon Source (EMuS), will be added to CSNS in the upgrading project. As a standalone facility located in a new...
CSNS (China Spallation Neutron Source) is a large scientific facility which was completed and entered in operation in March 2018. It is based on a high-power proton accelerator complex and is mainly for multidisciplinary research based on neutron scattering techniques. Other applications including muSR techniques have been considered from the beginning. The design study for an experimental...
The relationship between magnetism and superconductivity has been one of the most discussed topics in condensed matter physics. Within the BCS framework, magnetic impurities can act as pairing breaking agents rapidly suppressing superconductivity. However in unconventional superconductors, such as cuprates and iron-based superconductors, magnetic impurities may enhance superconductivity. In...
The Muon station for sciEnce, technoLOgy and inDustrY (MELODY) is foreseen to be the first muon source in China and to be located at the China Spallation Neutron Source in Dongguan. The stand-alone target station has been studied for the surface muons and the pions production. In this report, we aim to describe the design of the target station, including the mechanical design, the radiation...
