Showing papers by "Makina Yabashi published in 2004"
TL;DR: Cluster model calculations including charge transfer from doping-induced states show good agreement, confirming this picture of bulk properties reflected in Mn 2p core-levels using HX PES.
Abstract: Using hard x-ray (HX; hnu=5.95 keV) synchrotron photoemission spectroscopy (PES), we study the intrinsic electronic structure of La(1-x)Sr(x)MnO(3) (LSMO) thin films. Comparison of Mn 2p core-levels with soft x-ray (SX; hnu approximately 1000 eV) PES shows a clear additional well-screened feature only in HX PES. Takeoff-angle dependent data indicate its bulk (> or =20 A) character. The doping and temperature dependence track the ferromagnetism and metallicity of the LSMO series. Cluster model calculations including charge transfer from doping-induced states show good agreement, confirming this picture of bulk properties reflected in Mn 2p core-levels using HX PES.
121 citations
TL;DR: Hard x-ray valence band photoemission spectroscopy (PES) is realized using high-energy and high-brilliance synchrotron radiation.
Abstract: Hard x-ray valence band photoemission spectroscopy (PES) is realized using high-energy and high-brilliance synchrotron radiation. High-energy (∼6 keV) excitation results in larger probing depths of photoelectrons compared to conventional PES, and enables a study of intrinsic electronic property of materials in actual device structures much less influenced by surface condition. With this technique, requirements for surface preparation are greatly reduced, if not eliminated. It is a nondestructive tool to determine electronic structure from surface to genuine bulk as shown by a study on SiO2/Si(100). Electronic structure modification related to the ferromagnetism in the diluted magnetic semiconductor Ga0.96Mn0.04N is also observed.
84 citations
21 Jun 2004
TL;DR: A medium-length beamline with undulator source, BL20XU at SPring•8, was constructed, and opened to public use as discussed by the authors, where the distance from source point to the end of the beamline is 248 m.
Abstract: A medium‐length beamline with undulator source, BL20XU at SPring‐8, was constructed, and opened to public use. The distance from source point to the end of the beamline is 248 m. By utilizing the long beam transport path, the beamline has advantages for experiment that requires high spatial coherence in hard X‐ray regions.
67 citations
TL;DR: It is proposed that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy.
Abstract: Yb 3d and valence-band photoemission spectra of the first-order valence-transition compound YbInCu4 have been measured with hard x ray at an excitation energy of 5.95 keV. Abrupt changes are clearly observed in both spectra around the transition temperature T(V)=42 K, in comparison with ultraviolet and soft x-ray photoemission (VUV-PES and SX-PES) spectra. From the Yb 3d spectra, the Yb valence has been estimated to be approximately 2.90 from 220 down to 50 K and approximately 2.74 at 30-10 K. We propose that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy. On the other hand, the Yb2+ 4f-derived peaks in the valence-band spectra exhibit a remarkable enhancement below T(V). The shape of the valence-band spectra is different from those of the VUV-PES and SX-PES spectra above T(V), reflecting the In 5s and 5p contributions.
65 citations
TL;DR: In this article, the authors used synchrotron photoemission spectroscopy (PES) to study bulk electronic structure of the layered superconductor and showed that Co $2p$ core level spectra show well-separated ions.
Abstract: High-energy $(h\ensuremath{
u}=5.95\mathrm{keV})$ synchrotron photoemission spectroscopy (PES) is used to study bulk electronic structure of ${\mathrm{Na}}_{0.35}{\mathrm{CoO}}_{2}\ensuremath{\cdot}1.3{\mathrm{H}}_{2}\mathrm{O},$ the layered superconductor. In contrast to three-dimensional doped Co oxides, Co $2p$ core level spectra show well-separated ${\mathrm{Co}}^{3+}$ and ${\mathrm{Co}}^{4+}$ ions. Cluster calculations suggest low-spin ${\mathrm{Co}}^{3+}$ and ${\mathrm{Co}}^{4+}$ character, and a moderate on-site Coulomb correlation energy ${U}_{\mathrm{dd}}\ensuremath{\sim}3\char21{}5.5\mathrm{eV}.$ Photon dependent valence band PES identifies Co $3d$ and O $2p$ derived states, in near agreement with band-structure calculations.
38 citations
TL;DR: Mutual relations between figure errors and intensity uniformities of diverging X-ray beams have been investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes.
Abstract: A new figure correction method has been applied in order to fabricate an elliptical mirror to realize a one-dimensionally diverging X-ray beam having high image quality. Mutual relations between figure errors and intensity uniformities of diverging X-ray beams have also been investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes. By using a microstitching interferometer and elastic emission machining, figure correction of an elliptical mirror with a lateral resolution close to 0.1 mm was carried out. A one-dimensional diverging X-ray obtained using the fabricated mirror was observed at SPring-8 and evaluated to have a sufficiently flat intensity distribution.
28 citations
TL;DR: In this paper, the electronic structures of molecular beam epitaxy (MBE)-grown GaAs and GaN have been studied by means of a technique using a newly developed surface-insensitive probe, namely, high-resolution hard X-ray (HX) synchrotron radiation (hν= 5.95 keV) photoemission spectroscopy (PES).
Abstract: The electronic structures of molecular beam epitaxy (MBE)-grown GaAs and GaN have been studied by means of a technique using a newly developed surface-insensitive probe, namely, high-resolution hard X-ray (HX) synchrotron radiation (hν= 5.95 keV) photoemission spectroscopy (PES). The obtained valence band spectra and shallow core electronic states are compared with those calculated by the full-potential local density approximation (LDA) calculations explicitly including the Ga 3d core state. The experimental valence band spectra show a very good match with the calculations, simulated with linear combinations of the partial density of states. The Ga 3d core on d core states in GaN indicates a set of fine structures which are attributed to the Ga 3d-N 2s hybridization effect. The present experiments indicate that HX-PES provides an indispensable probe for investigating valence band electronic structures of materials, which has so far been impossible due to the limitations of proper surface preparation methods.
25 citations
18 citations
TL;DR: A new X-ray Michelson interferometer based on the BBB interferometers of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper and a further test carried out at the SPring-8 1 km beamline BL29XUL is reported.
Abstract: A new X-ray Michelson interferometer based on the BBB interferometer of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper. Here, a further test carried out at the SPring-8 1 km beamline BL29XUL is reported. One of the BBB's mirrors was displaced by a piezo to introduce the required path-length difference. The resulting variation of intensity with piezo voltage as measured by an avalanche photodiode could be ascribed to the phase variation resulting from the path-length change, with a small additional contribution from the change of the position of the lattice planes of the front mirror relative to the rest of the crystal. This 'Michelson fringe' interpretation is supported by the observed steady movement across the output beam of the interference fringes produced by a refractive wedge when the piezo voltage was ramped. The front-mirror displacement required for one complete fringe at the given wavelength is only 0.675 A; therefore, a quiet environment is vital for operating this device, as previous experiments have shown.
14 citations
TL;DR: In this paper, a high-resolution monochromator at $E=14.41\mathrm{keV}$ was developed for enhancing the interference signal, and transverse coherence profiles of undulator radiation were evaluated from measurements of mode numbers.
Abstract: Intensity interferometry has been performed for the study of x-ray coherence. A high-resolution monochromator at $E=14.41\mathrm{keV}$ was developed for enhancing the interference signal. Transverse coherence profiles of undulator radiation were evaluated from measurements of mode numbers. The obtained coherence length in vertical, which is perpendicular to the scattering plane of the monochromator, was proportional to the distance from the light source, as is expected from the Van Cittert--Zernike theorem. Vertical emittances of the storage ring were determined from the measured coherence lengths. Degradation of transverse coherence with phase object was measured and analyzed based on the propagation law of mutual intensity.
Journal Article•
TL;DR: In this paper, the temperature dependences of the Yb 4f and 3d states of Kondo semiconductor YbB 12 single crystal have been studied by high-resolution photoemission spectroscopy taken at hν =100 and 5951 eV.
Abstract: The temperature dependences of the Yb 4f and 3d states of Kondo semiconductor YbB 12 single crystal have been studied by high-resolution photoemission spectroscopy taken at hν =100 and 5951 eV. The Yb 2+ 4f 7/2 state at the Fermi level is enhanced on cooling. With improved energy resolution, we discover an additional quasi-particle peak at 15 meV that developes below 60 K. From the Yb 3d spectrum at 22 K, the Yb valence is estimated to be∼2.88.
TL;DR: In this paper, the results of non-resonant magnetic x-ray diffraction measurements of the metamagnet FeCl2·2H2O subjected to an applied magnetic field, H, are reported.
Abstract: The results of non-resonant magnetic x-ray diffraction measurements of the metamagnet FeCl2·2H2O subjected to an applied magnetic field, H, are reported. The material shows two successive first-order phase transitions: at Hc1 = 3.62 T from the antiferromagnetic (AF) to intermediate (I) phases, and at Hc2 = 4.67 T from phase I to a ferromagnetic phase at low temperatures. We find that the AF and I phases coexist over a wide range of H below Hc1, when H is decreased from the I phase. We were able to follow the evolution of the AF and I domains with the change of H. The coexistence appears not to come from demagnetizing effects, and instead reflects the intrinsic nature of the material.
21 Jun 2004
TL;DR: Beryllium windows were characterized using coherent x-rays at the one-kilometer beamline of SPring-8.1 as discussed by the authors, showing that the non-uniformity of transmission x-ray images is largely due to Fresnel diffraction from deficiencies such as surface pits with diameter of order of one micron to ten microns, having no correlation with averaged surface roughness measured with an optical profilometer.
Abstract: Beryllium windows were characterized using coherent x‐rays at the one‐kilometer beamline of SPring‐8. Non‐uniformity of transmission x‐ray images is largely due to Fresnel diffraction from deficiencies such as surface pits with diameter of order of one micron to ten microns, having no correlation with averaged surface roughness measured with an optical profilometer.
13 Jan 2004
TL;DR: In this paper, the authors developed an ultra-precise fabrication system for x-ray optics, which combined numerically controlled plasma CVM and EEM, and achieved nanometer order form accuracy having atomic order roughness.
Abstract: We developed ultra-precise fabrication system for x-ray optics, which combined numerically controlled plasma CVM and EEM. In this system, nanometer order form accuracy having atomic order roughness is achieved. And there are no deformed layers on the surface because these fabrication processes utilizes chemical reaction. So, this system is effective for not only reflective optics but also for diffractive optics. Recently, elliptical mirrors having less than 3 nm form accuracy are fabricated by utilizing the above system, and K-B arrangement microfocusing unit for installation of these mirrors are developed. In this unit, micro x-ray beam having the size of 180 (V) 290 (H) nm is achieved at 15 keV. By scanning irradiation of the micro x-ray beam and by detecting x-ray fluorescence, inside structures of some mammalian cells are observed with resolution of 0.2 µ m. Keywords : plasma CVM(Chemical Vaporization Machining), EEM(Elastic Emission Machining), x-ray mirror, elliptical mirror, Kirkpatrick-Baez, coherent x-ray, microfocusing, x-ray fluorescence
TL;DR: In this paper, X-ray diffraction measurements on a spin-Peierls material CuGeO 3 in applied magnetic fields, H, up to 15 T are made, and they find that the temperature, T, dependence of the incommensurate Bragg peak at a lower H is quite different from that at a higher H.
Abstract: Synchrotron X-ray diffraction measurements on a spin–Peierls material CuGeO 3 in applied magnetic fields, H , up to 15 T are made. We find that the temperature, T , dependence of the incommensurate Bragg peak at a lower H is quite different from that at a higher H . At sufficiently high fields, we find that the lattice incommensurability, δ l , is almost independent of T , while at H slightly above the critical field = 12.25 T for the commensurate to incommensurate transition, δ l decreases with increasing T . We interpret that this finding is due to a stabilization of the incommensurate state by a strong magnetic field which suppresses thermal fluctuations.
TL;DR: In this paper, the Yb 3d and valence-band photoemission spectra of YbInCu 4 have been measured at hν =5.95 keV.
Abstract: Yb 3d and valence-band photoemission spectra of YbInCu 4 have been measured at hν =5.95 keV. Abrupt changes are observed in both spectra, reflecting the valence transition at Tν =42 K. The Yb valence estimated from the Yb 3d spectra is z ∼2.90 at 220–50 K and sharply decreases to z ∼2.74 at 30–10 K.
18 Oct 2004
TL;DR: In this article, a microstitching interferometry based on a microscopic interferometer having peak-to-valley (p-v) height accuracy of sub-nanometer order and lateral resolution higher than 20 mm was developed to measure surface figures of X-ray mirror optics.
Abstract: Metrology plays more important role than machining in surface figuring at sub-nanometer accuracy The microstitch-ing interferometry based on a microscopic interferometer having peak-to-valley (p-v) height accuracy of sub-nanometer order and lateral resolution higher than 20 mm was developed to measure surface figures of X-ray mir-ror optics In addition, the relative angle determinable stitching interferometry was also developed to measure surface profiles of elliptical mirrors to realize hard X-ray nanofocusing By combining the two interferometies, the absolute measurement accuracy of approximately 3 nm (peak-to-valley) was achieved in the measurement of a cylindrical sur-face having the same curvature as the elliptically designed shape to enable nanofocusing
13 Jan 2004
TL;DR: In this article, a new figure correction method was applied to fabricate an elliptical mirror to realize a one-dimensionalally diverging X-ray beam having high image quality.
Abstract: A new figure correction method is applied to fabricate an elliptical mirror to realize a one-dimensionally diverging X-ray beam having high image quality. Mutual relations between figure errors and intensity uniformities of diverging X-ray beams are also investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes. By using the microstitching interferometer and elastic emission machining, figure correction of an elliptical mirror with lateral resolution close to 0.1mm was carried out. A one-dimensional diverging X-ray obtained by the fabricated mirror was observed at SPring-8 and evaluated to have a sufficiently flat intensity distribution.
18 Oct 2004
TL;DR: In this paper, the authors realized a hard X-ray focused beam having a 180nm×90nm focal size using fabricated elliptical mirrors with platinum-coated surfaces.
Abstract: In our previous study, we realized a hard X-ray focused beam having a 180nm×90nm focal size using fabricated ellip-tical mirrors. In this study, to realize a smaller focal size, more steeply curved elliptical mirrors with platinum-coated surfaces were fabricated. We showed that aspheric quality mirrors can be manufactured with recently developed ma-chining methods. We carried out line focusing tests on the elliptical mirror at the 1-km-long beamline of SPring-8. A full width at half maximum of 40 nm was achieved in the focal beam profile under the best focusing conditions.
18 Oct 2004
TL;DR: In this paper, a focusing unit with the adjusting mechanism fulfilling the required alignment accuracies was constructed, and the relationships between the alignment errors and focused beam profiles were quantitatively examined at the 1km-long beamline (BL29XUL) of SPring-8.
Abstract: The spatial resolution of the scanning X-ray microscopy apparently depends on the beam size of the focused X-ray. Recently, highly accurate elliptical mirrors were reported to be fabricated, and nearly diffraction-limited line focusing was achieved. In this study, to realize diffraction-limited and 2-dimentional focusing with such highly accurate mirrors, accuracies to be realized in mirror alignings, for example, adjusting the glancing angle and the in-plane rotation, were estimated by employing two types of simulators. They are appropriately based on geometrical or wave-optical theories. They are alternatively employed according to the degree of accuracy required in the mirror alignment. A focusing unit with the adjusting mechanism fulfilling the required alignment accuracies was constructed, and the relationships between the alignment errors and focused beam profiles were quantitatively examined at the 1km-long beamline (BL29XUL) of SPring-8. Obtained results were in good agreement with the calculated results. Additionally, the alignment accuracy to be realized in the K-B unit equipping mirrors of larger NA (numerical aperture) was calculated to realize sufficient performances in focusing.
TL;DR: In this paper, the resonant inelastic X-ray scattering (RIXS) was measured for an insulating SrCuO2 with changing the incident photon energy (hν) near the Cu 1s absorption edge (K-edge).