Quantum Beam Science

Polarized neutron reflectometry (PNR) analyzes surface and interfacial structures of materials. For the SHARAKU reflectometer at the Materials and Life Science Experimental Facility in the Japan Proton Accelerator Research Complex, precise measurements under weak magnetic fields, which are critical for modern spintronics, have long been challenging. To address this issue, we developed a precise weak-field sample environment equipped with a newly designed coil system. The magnetic field at the sample position can be applied within the surface/interface plane, either in the scattering plane (horizontal configuration) or perpendicular to it (vertical configuration). The horizontal configuration achieved high polarization efficiency across a stable field range, whereas the vertical configuration enabled the experiments to cross zero into negative fields. We demonstrated the instrument’s capability by resolving the remanent magnetic structure of an Fe film. Its applicability to soft matter was proven through analysis of a cellulose thin film with roughness using magnetic contrast variation PNR. In this case, precise weak-field control is essential to tune the magnetic contrast from the reference layer beneath the soft film. These results establish the system as a versatile platform for future PNR and polarized off-specular scattering experiments across a wide range of materials.

The NELIPS acronym stands for Nano-Enhanced Laser-Induced Plasma Spectroscopy. Within this framework, the temporal variation in the enhanced plasma emissions from pure nanomaterials with respect to corresponding bulk materials was monitored as a function of delay time in the range from 1 to 5–11 μs. Six different pure nanomaterials were employed including silver, zinc, aluminum, titanium, iron, and silicon. Radiation from pulsed Nd: YAG laser at wavelength 1064 nm was used to induce both bulk and pure nanomaterial plasmas under similar experimental conditions. Plasma emissions from both targets were monitored via optical emission spectroscopy technique (OES). The spectral line intensities (Signal-To-Noise ratio S/N) from the pure nanomaterial plasma turns out to decline in a constant logarithmic manner but at a slower rate than that from the corresponding bulk material plasma. Consequently, the measured average enhanced emission from different nanomaterials features an increase in an exponential manner with delay time. This trend of increase was accounted for via mathematical elaboration of enhanced emission based on the measured Signal-To-Noise data. Plasma parameters (electron density and temperature) were precisely measured at each delay time as well.

Japanese swords have a history of more than one thousand years and are recognized as metallic art objects. The sword-making process is not clearly understood, especially for old swords made before about 1600 A.D. Knowledge of structural information such as crystallite sizes and anisotropy is important to understand the sword characteristics and the sword-making process. Bragg-edge transmission imaging is a useful noninvasive method that can extract this structural information continuously over a wide area of the sword. Neutron CT is powerful enough to detect quenched areas, voids, and precipitates. Using both methods, we measured more than 10 swords and obtained information on the two-dimensional crystallite size distribution, anisotropy parameter, lattice plane spacing, and quenched regions. Comparison of the results indicated the following features: the crystallite size distributions showed two patterns: an almost uniform distribution of small-sized crystallites, and mixed distributions of large- and small-sized crystallites. The patterns were observed in different eras and places. The preferred orientation showed different patterns, and strain areas due to quenching were observed in many swords. The quenched area showed a trend that the quenching was weaker for old swords than newer ones. CT images showed the boundaries of the quenched regions and a void in the layered structure for one sword, for which a layered structure was confirmed.