SPring-8/SACLA Research Report

　The Ce 4f electronic state of weak ferromagnet CeIr₃B₂ which has a relatively high Curie temperature among Ce compounds is studied by magnetic circular dichroism in the Ce 3d absorption. The result is compared with other Ce compounds and also the orbital and spin Ce magnetic moments are estimated through a tentative sum-rule analysis.

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　The electronic band structure of a ferromagnet CeRh₃B₂ which has a very high Curie temperature among the Ce compounds is studied by angle resolved photoemission (ARPES). The inner potential has been determined by comparing the ARPES result with the band structure calculation. The dispersion along the Γ-Z direction was further compared with the band structure calculation.

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　In this study, we investigated the thermal effect on the electronic properties of the commercial Cu(In,Ga)(Se,S)₂ (CIGSeS)-based solar cell by using a nondestructive method, hard X-ray photoemission spectroscopy (HAXPES). The samples were individually air annealed to 60 °C, 120 °C and 180 °C in a quartz tube for 48 hrs. The ZnO layer was etched to form a gradient thickness by HCl (0.1%) for depth information. The quantitative analysis of the HAXPES results shows that all of the elements in the surface region of the CIGSeS absorber layer were upwardly diffused and, for CdS buffer layer, the sulfur atoms exhibit an upward diffusion after thermal treatment. The thermal annealing treatment accelerates the disappearance of the ordered defect compounds (ODC) domains and the elemental interdiffusion at the ZnO/CdS/CIGSeS interfaces, further leading to a decrease of the short current density.

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　Relentless effort for three decades to uncover the mechanism of high-temperature superconductivity has passed. Progress has, to a large degree, been held back by the difficulty to probe the low-temperature normal state. This non-superconducting ground state is believed to hold the key to this longstanding enigma. Here, we reported x-ray diffraction experiments performed at SACLA free-electron laser under pulsed magnetic fields capable of reaching the normal state. For the primary purpose, our measurements were designed to search for field-induced charge ordering in prototypical cuprate material La_2-xSr_xCuO₄ (x = 12 and 14.5 %). However, due to large background scattering, we were unable to successfully resolve the intensity from the charge order reflections. Instead, we observed a magnetostriction effect Δc/c as large as 10^-5 which increases linearly proportional to H ². This observation calls for further lab-based magnetostriction measurement as the c-axis lattice parameter may be an important tuning parameter for superconducting transition temperature T_c, via orbital distillation scenario.

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