H.J. Im

BL5U at UVSOR‐II for Three‐dimensional Angle‐resolved Photoemission Spectroscopy

BL5U at UVSOR‐II has been reconstructed in 2004’s for three‐dimensional angle‐resolved photoemission (3D‐ARPES) study on solids and surfaces. The beamline is equipped with a helically/linearly polarized undulator, an old‐type monochromator named as SGM‐TRAIN designed in 1995’s, and a new photoemission end‐station. Since their performances are insufficient to study anomalous electronic/magnetic properties on materials in recent years, we reconstructed the beamline for a high‐resolution study as follows; (1) The manipulation of the pre‐focusing mirror was updated to a high‐precision system controlled by pulse‐motors. (2) The entrance slit with water cooling system was adopted for avoiding the heat load from undulator radiation. (3) The SGM‐TRAIN was re‐arranged to the optimum condition to the undulator light. (4) The free tuning program of the undulator gap and monochromator‐control systems was introduced. Due to the reconstructions, we successfully improved the throughput intensity and energy resolution of...

Transport properties in low carrier system CeTe2

Abstract The resistivity and Hall constant are measured for stoichiometry single crystals of LaTe 2 and CeTe 2 . A strong anisotropy appears in the resistivity. In high temperature regions their carrier concentrations are independent of temperature. The mobility of CeTe 2 has a temperature dependence which is similar to that of the Kondo system. The anisotropy in the crystal field interaction is found and can be reasonably explained by the p–f mixing.

Single crystal growth and magnetic, optical, and photoelectrical properties of EUO thin film

We report on the single-crystal growth of EuO thin films [fcc 1×1 (100)] and their magnetic, optical, and photoelectrical properties to examine the consistency with the bulk materials. EuO thin films were fabricated on a BaO buffer layer created on a SrTiO3 substrate. The obtained EuO thin film was found to be a ferromagnetic semiconductor with a Curie temperature of 71 K and an energy gap of about 1 eV. We were able to observe a clear angle dependence of the photoemission spectrum, indicating good single-crystalline properties.

Magnetic-field-induced superconductor-insulator-metal transition in an organic conductor : An infrared magneto-optical imaging spectroscopic study

The magnetic-field-induced superconductor-insulator-metal transition (SIMT) in partially deuterated

Infrared spectroscopy under multiextreme conditions : Direct observation of pseudogap formation and collapse in CeSb

\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{C}\mathrm{N})}_{2}]\mathrm{Br}

Magnetic and transport properties of the antiferromagnetic dense Kondo lattice system Ce2CuxNi1−xGe6

, which is just on the Mott boundary, has been observed using the infrared magneto-optical imaging spectroscopy. The infrared reflectivity image on the sample surface revealed that the metallic (or superconducting) and insulating phases coexist and they have different magnetic-field dependences. One of the magnetic-field dependence is SIMT that appeared on part of the sample surface. The SIMT was concluded to originate from the balance of the inhomogeneity in the sample itself and the disorder of the ethylene end groups resulting from fast cooling.

Fermi Surface Variation of Ce 4f-electrons in Hybridization Controlled Heavy-Fermion Systems

Infrared reflectivity measurements of CeSb under multi-extreme conditions (low temperatures, high pressures and high magnetic fields) were performed. A pseudo gap structure, which originates from the magnetic band folding effect, responsible for the large enhancement in the electrical resistivity in the single-layered antiferromagnetic structure (AF-1 phase) was found at a pressure of 4 GPa and at temperatures of 35 - 50 K. The optical spectrum of the pseudo gap changes to that of a metallic structure with increasing magnetic field strength and increasing temperature. This change is the result of the magnetic phase transition from the AF-1 phase to other phases as a function of the magnetic field strength and temperature. This result is the first optical observation of the formation and collapse of a pseudo gap under multi-extreme conditions.

Crystalline electric field effects in Ce 3d core-level spectra of heavy-fermion systems: Hard x-ray photoemission spectroscopy on CeNi1―xCoxGe2

Abstract The magnetic susceptibility, the magnetization and the electrical resistivity of new materials Ce 2 Cu x Ni 1− x Ge 6 have been measured. It is found that Ce 2 Cu x Ni 1− x Ge 6 is an antiferromagnetic dense Kondo lattice system which competes with RKKY interaction. The competition is dependent on the change of the lattice volume, which gives rise to the change of hybridization.

Hybridization gap collapse at a quantum critical point of CeNi1-xCoxGe2

Abstract Ce 3d–4f resonant angle-resolved photoemission measurements on CeCoGe 1.2 Si 0.8 and CeCoSi2 have been performed to understand the Fermi surface topology as a function of hybridization strength between Ce 4f- and conduction electrons in heavy-fermion systems. We directly observe that the hole-like Ce 4f-Fermi surfaces of CeCoSi2 is smaller than that of CeCoGe 1.2 Si 0.8 , indicating the evolution of the Ce 4f-Fermi surface with the increase of the hybridization strength. In comparison with LDA calculation, the Fermi surface variation cannot be understood even though the overall electronic structure is roughly explained, indicating the importance of strong correlation effects.

Hybridization gap collapse at a quantum critical point of CeNi1-xCoxGe2CeNi1-xCoxGe2

High-resolution hard X-ray photoemission measurements have been performed to clarify the electronic structure originating from the strong correlation between electrons in bulk Ce 3