Kenta Amemiya

We study spin magnetic moments near half-metallic Co2FexMn1−xSi (CFMS)/metal interfaces using depth-resolved x-ray magnetic circular dichroism (XMCD) and analyze their robustness against thermal fluctuations. We prepare epitaxial magnetic multilayered films with CFMS/CoFe and CFMS/Ag interfaces and observe the x-ray absorption spectroscopy (XAS) and XMCD spectra for both the interfacial and inner CFMS regions. By analyzing the observed XAS and XMCD spectra, we approximately extract the Mn-related magnetic moments. The results show that the Mn spin magnetic moment at the CFMS/CoFe interface exhibits almost no reduction compared with that in the inner CFMS layer, in contrast to the significant reduction observed at the CFMS/Ag interface. This suggests that the CFMS/CoFe interface provides a larger interfacial exchange stiffness than the CFMS/Ag interface, consistent with theoretical interface exchange stiffness values obtained from first-principles calculations. Furthermore, the large exchange stiffness at the CFMS/CoFe interface leads to the high stability of local spin magnetic moments to thermal fluctuation, resulting in a weaker temperature dependence of the magnetoresistance (MR) ratio in current-perpendicular-to-plane giant MR devices with a CoFe/CFMS/Ag/CFMS/CoFe structure than in those with a CFMS/Ag/CFMS structure.

Magnetic anisotropy study of the skyrmionic and textured MnSi thin films, demonstrated using angle-dependent X-ray magnetic circular dichroism (XMCD) and X-ray near-edge spectroscopy (XANES).

We report the development and initial applications of the multi-functional research and development beamlines BL-11A and BL-11B at the Photon Factory, which are designed to enable simultaneous use of hard and soft x-rays. The two beamlines share a common bending-magnet source and deliver independently monochromatized hard- and soft-x-ray beams that can be focused onto the same sample position in a downstream experimental hutch, providing a versatile platform for two-beam experiments in which hard and soft x-rays can serve as pump and/or probe beams in various combinations. As proof-of-concept demonstrations, we performed probe–probe measurements of water electrolysis on a cobalt electrocatalyst and pump–probe measurements of x-ray-induced dissociation of a caged compound. In the probe–probe scheme, hard- and soft-x-ray absorption spectroscopy was carried out simultaneously to track correlated changes in the catalyst oxidation state and oxygen-related intermediates during the oxygen evolution reaction. In the pump–probe scheme, chemical changes in 2-iodosobenzoic acid induced by hard-x-ray excitation at the iodine L3 edge were monitored using soft-x-ray absorption spectroscopy at the oxygen K edge.

Nickel ferrite (NiFe ₂ O ₄ ) and ZrC-based composites were synthesized and characterized through structural, morphological, spectroscopic, and magnetic analyses to investigate the influence of ZrC incorporation on their magnetic behaviour.

Nanocrystalline Ru1−xIrxO2 catalysts with particle size between 4 and 10 nm were prepared by microwave-assisted hydrothermal reaction from ruthenium chloride and iridium acetate. Prepared materials were single-phase solid solutions conforming to the rutile structural type with random mixing of both cations in the lattice positions. Mixing Ru and Ir in the rutile structure leads to synergetic improvement of the catalyst activity in oxygen evolution in acid media with a distinct maximum of the activity at a composition conforming to Ru0.5Ir0.5O2. The quantum chemical characterization of the prepared materials attributes the observed activity improvement to the ability of Ru-Ir-O catalysts to activate the bridge position, breaking the scaling relationships. This allows to optimize the OER catalytic activity beyond the top of the volcano. The DFT calculations also suggest that the activity improvement is caused by a minor fraction of the active sites at the catalyst surface, while the majority of the surface sites (∼50 %) remains inactive even at 1.7 V vs. RHE. The viability of the DFT proposed reaction mechanism is confirmed by in-situ soft X-ray absorption spectroscopy, which identifies Ru in cus positions as the primary site starting the oxygen evolution. The catalytic cycle starting on cus Ir sets in at ca. 100 mV higher potentials. The activation of the bridge positions presents itself as a weak negative signal at 531 eV observed in differential spectra under oxygen evolution conditions.

Enhanced magnetism and correlation-driven electronic effects in SrRuO ₃ nanoparticles demonstrated through X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD), and resonant photoemission spectroscopy (RPES).

Charge transfer between perylene and bromine molecules and the effect of the top-contact gold layer were studied using X-ray absorption fine structure spectroscopy near the carbon and bromine K edges (C K and Br K NEXAFS). Bromine molecules construct a [[EQUATION]]-complex with perylene molecules in the form of Br3–, as confirmed by the Br K NEXAFS spectrum showing an intermediate spectral shape between Br2 and Br–. The polarization dependent analysis for the [[EQUATION]]–form perylene single crystal, in which the molecular plane is directed up with respect to the substrate, suggests that majority of the Br3– anions was directed up. The [[EQUATION]]–complex became unstable when evacuated and bromine substitution reaction proceeded, presenting characteristic spectral features of Br–C bonds in both the Br and C K NEXAFS spectra. The Br-substituted perylene formed a charge-transfer complex in a similar manner as the unsubstituted perylene, and the vacant state in the perylene molecules was confirmed by the 1s to singly unoccupied molecular orbital (SUMO) transition at the absorption edge in the C K NEXAFS spectrum. The SUMO at the top-contact gold interface was filled with Au electrons and remained unoccupied in the bulk, as confirmed by the probing depth-dependent spectra.

Depth-resolved characterization of buried magnetic interfaces is vital for advancing spintronic devices, yet consistent analysis remains challenging. Fluorescence-yield depth-resolved X-ray magnetic circular dichroism (XMCD) enables quantitative profiling of spin and orbital moments, but conventional background (BG) subtraction is empirical and operator-dependent. We present a systematic framework using unsupervised t-distributed stochastic neighbor embedding similarity mapping to automate and optimize BG subtraction. Validation tests confirm robustness against spectral noise while revealing strong sensitivity to BG subtraction, highlighting the critical role of optimized BG treatment. Applied to a Graphene/L1 ₀ -FePd thin film, the method reproduces interfacial spin suppression and orbital enhancement with expert-level consistency. This framework thus provides a standardized and reproducible approach to depth-resolved XMCD, broadly applicable to interfacial magnetism in spintronic materials.