Development of a non-destructive depth-selective quantification method for sub-percent carbon contents in steel using negative muon lifetime analysis.

The amount of C in steel, which is critical in determining its properties, is strongly influenced by steel production technology. We propose a novel method of quantifying the bulk C content in steel non-destructively using muons. This revolutionary method may be used not only in the quality control of steel in production, but also in analyzing precious steel archaeological artifacts. A negatively charged muon forms an atomic system owing to its negative charge, and is finally absorbed into the nucleus or decays to an electron. The lifetimes of muons differ significantly, depending on whether they are trapped by Fe or C atoms, and identifying the elemental content at the muon stoppage position is possible via muon lifetime measurements. The relationship between the muon capture probabilities of C/Fe and the elemental content of C exhibits a good linearity, and the C content in the steel may be quantitatively determined via muon lifetime measurements. Furthermore, by controlling the incident energies of the muons, they may be stopped in each layer of a stacked sample consisting of three types of steel plates with thicknesses of 0.5 mm, and we successfully determined the C contents in the range 0.20-1.03 wt% depth-selectively, without sample destruction.

Non-destructive 3D imaging method using muonic X-rays and a CdTe double-sided strip detector.

Elemental analysis based on muonic X-rays resulting from muon irradiation provides information about bulk material composition without causing damage, which is essential in the case of precious or otherwise unreachable samples, such as in archeology and planetary science. We developed a three-dimensional (3D) elemental analysis technique by combining the elemental analysis method based on negative muons with an imaging cadmium telluride double-sided strip detector (CdTe-DSD) designed for the hard X-ray and soft [Formula: see text]-ray observation. A muon irradiation experiment using spherical plastic samples was conducted at the Japan Proton Accelerator Research Complex (J-PARC); a set of projection images was taken by the CdTe-DSD, equipped with a pinhole collimator, for different sample rotation angles. The projection images measured by the CdTe-DSD were utilized to obtain a 3D volumetric phantom by using the maximum likelihood expectation maximization algorithm. The reconstructed phantom successfully revealed the 3D distribution of carbon in the bulk samples and the stopping depth of the muons. This result demonstrated the feasibility of the proposed non-destructive 3D elemental analysis method for bulk material analysis based on muonic X-rays.

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters.

Dimensionality is a critical factor in determining the properties of solids and is an apparent built-in character of the crystal structure. However, it can be an emergent and tunable property in geometrically frustrated spin systems. Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet, pharmacosiderite, via muon spin resonance and neutron scattering. We find that the spin correlation exhibits a two-dimensional characteristic despite the isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe3+ ions in the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation by geometrical frustration based on spin wave calculations. Moreover, we suggest that even one-dimensionalisation occurs in the decoupled layers, generating low-energy and one-dimensional excitation modes, causing large spin fluctuation in the classical spin system. Pharmacosiderite facilitates studying the emergence of low-dimensionality and manipulating anisotropic responses arising from the dimensionality using an external magnetic field.

A novel challenge of nondestructive analysis on OGATA Koan's sealed medicine by muonic X-ray analysis.

OGATA Koan (1810-63) was a physician and the director of Tekijuku, and he contributed to Western medicine in the late Edo period. Osaka University preserves two of his medicine chests. One of the chests, which was used in his last years (the second chest) contained 22 glass bottles and 6 wooden cylinders. These bottles and cylinders contained formulated medicines; however, about half cannot be opened because of the long-term storage. It is necessary to comprehend the physical property of both the containers and their contents for investigation of this adequate preservation method; however, destructive analysis is not allowed. To analyze the medicines sealed in the glass bottles, we focused on muonic X-ray analysis, which has high transmittance. First, we certified the analytical methods using a historical medicinal specimen preserved in Osaka University. Thereafter, we applied the method on the bottles stored in the second chest. X-ray fluorescence identified the glass of those bottles to be lead potash glass. Among these bottles, we chose the bottle with the label "," which contains white powdered medication, for muonic X-ray analysis. We identified the contents of the medication in the glass to be Hg2Cl2. Through this study, we first applied muonic X-ray analysis on the medical inheritances and succeeded to detect the elements contained both in the container and in the contents of the sealed bottle. This would be a new method for nondestructive analysis of such cultural properties.

Nondestructive High-Sensitivity Detections of Metallic Lithium Deposited on a Battery Anode Using Muonic X-rays.

Metallic Li deposited on the anode is known to induce short circuiting and degradation of the charge capacity of Li-ion batteries. However, no reliable technique is currently available to observe such Li metal without removing the case of the battery. An elemental analysis using muonic X-rays is proposed here because of its unique properties of nondestructive measurement, high sensitivity to light elements, and depth resolution. We demonstrated that this technique can be applied to detection of Li deposited on the surface of an anode containing Li ions, using a fully charged anode with Li deposited due to overcharge in an Al-laminated plastic pouch. The basis for the detection method is the difference in the atomic Coulomb capture ratio of the negative muons between the Li metal and ions. We have found, as a result, that the intensity of the muonic X-rays from metallic Li was approximately 50 times higher than that from Li ions. Consequently, the Li metal on the anode was clearly distinguishable from the intercalated Li ions in the anode. Furthermore, measurements of two overcharged anodes with 1.3 and 2.7 mg of metallic Li deposition, respectively, indicated that this technique is suitable for quantitative analysis. Distribution analysis is also possible, as shown by a preliminary observation on an overcharged anode from the back side. Therefore, this technique offers a new approach to the analysis of Li deposited on the anode of a Li-ion pouch battery.

Nuclear Magnetic Field in Solids Detected with Negative-Muon Spin Rotation and Relaxation.

Using an intense negative muon (µ^{-}) source, we have studied the internal magnetic fields in a powder sample of magnesium hydride (MgH_{2}). By extracting the signal from the µ^{-} captured on Mg nuclei, we found that the negative muon spin rotation and relaxation (µ^{-}SR) spectra clearly showed a Kubo-Toyabe-type relaxation, which indicates a random magnetic field at the Mg site. The field distribution width obtained is very consistent with the predicted value at the Mg site estimated by dipole field calculations, supporting our claim to have observed the nuclear magnetic fields of hydrogens in MgH_{2}. As is the case with µ^{+}SR, µ^{-}SR promises to soon be an indispensable tool for materials analyses.

All-in-all-out magnetic domains: x-ray diffraction imaging and magnetic field control.

Long-range noncollinear all-in-all-out magnetic order has been directly observed for the first time in real space in the pyrochlore Cd_{2}Os_{2}O_{7} using resonant magnetic microdiffraction at the Os L_{3} edge. Two different antiferromagnetic domains related by time-reversal symmetry could be distinguished and have been mapped within the same single crystal. The two types of domains are akin to magnetic twins and were expected-yet unobserved so far-in the all-in-all-out model. Even though the magnetic domains are antiferromagnetic, we show that their distribution can be controlled using a magnetic field-cooling procedure.

Resonant x-ray diffraction study of the strongly spin-orbit-coupled mott insulator CaIrO3.

We performed resonant x-ray diffraction experiments at the L absorption edges for the post-perovskite-type compound CaIrO(3) with a (t(2g))^{5} electronic configuration. By observing the magnetic signals, we could clearly see that the magnetic structure was a striped ordering with an antiferromagnetic moment along the c axis and that the wave function of a t(2g) hole is strongly spin-orbit entangled, the J(eff)=1/2 state. The observed spin arrangement is consistent with theoretical work predicting a unique superexchange interaction in the J(eff)=1/2 state and points to the universal importance of the spin-orbit coupling in Ir oxides, independent of the octahedral connectivity and lattice topology. We also propose that nonmagnetic resonant scattering is a powerful tool for unraveling an orbital state even in a metallic iridate.

Magnetic ground-state of perovskite PbVO3 with large tetragonal distortion.

The magnetic properties of PbVO 3, a PbTiO 3-type perovskite with a large tetragonal distortion ( c/a = 1.229), were investigated. The temperature dependence of the measured magnetization of multidomain single-crystal samples showed a broad maximum centered around 180 K, indicating a two-dimensional antiferromagnetism. muSR measurement revealed the presence of a long-range order below 43 K. The two-dimensional magnetism is due to the ordering of d xy orbitals, which is thought to also be related to the large tetragonal distortion of PbVO 3.