Masami Yoshizawa

Trial use of carbon‐fiber‐reinforced plastic as a non‐Bragg window material of x‐ray transmission

The carbon‐fiber‐reinforced plastic (CFRP) that can be used for window material in place of beryllium is a composite‐type material comprising twisted carbon fibers and bisphenol‐A plastic. Since the constituent elements of hydrogen, carbon, and nitrogen are thoroughly dispersed as a compound, the mass absorption coefficient of CFRP is somewhat larger than that of beryllium. The diffraction pattern of CFRP shows only a single halo pattern without a Bragg‐like peak which is found in Mylar. Through x‐ray diffraction, CFRP was confirmed to be practical for use as a non‐Bragg window material with a moderately low mass‐absorption coefficient and could be substituted for crystalline beryllium.

X-ray Interference Fringe in Bragg–(Bragg)m–Laue Case from Thin Finite Crystal

In an absorbing thin finite crystal, part of the incident X-rays can be confined in the Bragg–(Bragg)m–Laue case. The confined beams are repeatedly diffracted in the crystal and come out of its edge surface. An X-ray interference fringe, which is caused by a sequence of diffractions between the top and bottom surfaces during the confinement, is observed in the beams emitted in both the reflection and transmission directions. The characteristic features of the fringe measured using synchrotron radiation are studied.

X-rays beam condensation by confinement in a thin crystal

We have observed condensation of X-rays emitted from an edge of a thin Ge parallel crystal, using X-rays from synchrotron radiation. When highly parallel X-rays with the energy near an absorption edge of an atom or a nucleus are incident on a thin crystal in the Bragg case, a part of X-rays is confined in the crystal and do not come out either from the top or the bottom surface. The density of confined beam increases as the width of the incident beam is increased. The confined beam can come out from an edge of a thin crystal with higher density than the incident beam.

X-ray dynamical diffraction in Ge with a zero-real-part scattering factor

X-ray dynamical diffraction induced only by the imaginary part of the scattering factor was measured using a Ge perfect crystal. The 844 integrated reflecting intensities near the K-absorption edge were measured in both the Bragg and the Laue cases. The intensities show the characteristic variations for the scattering factor having no real part, which agree well with theoretical predictions. There remains a slight difference between the theoretical [Fukamachi & Kawamura (1993). Acta Cryst. A49, 384–388] and the experimental energy position at which this occurs, which is related to the fine structure of the anomalous scattering factor above the absorption edge.

Formation of interference fringes in the Bragg-(Bragg)m-Laue mode.

X-ray interference fringes in the beams diffracted from a lateral surface of a thin plane-parallel crystal are measured and analyzed using Wagners approach [Wagner (1956), Z. Phys. 146, 127-168]. It is found that the fringes are caused by the interference between the internal waves excited by the incident beam in both the Bragg-Laue case and the Bragg-Bragg-Laue case. The period of the interference fringes is shown to be proportional to the distance between the incident point of the X-ray and the crystal edge, and to be inversely proportional to the crystal thickness.

Measurement of X-ray rocking curves in the Bragg-Laue case.

X-ray rocking curves in the Bragg-Laue case diffracting from the side surface of a plane-parallel crystal have been measured using a high-resolution optical system. The full width at half-maximum of the rocking curves is approximately three times narrower than that measured from the top surface. The characteristics of the transmitted beam from the side surface are almost the same as those through a thin crystal in the Bragg case. The rocking curves and the direction of X-ray energy flow in the crystal observed in the experiment can be reproduced using Wagners approach [Wagner (1956), Z. Phys. 146, 127-168].

Interference fringes in multiple Bragg-Laue mode and mirage fringes from bent crystals.

Interference fringes are measured in the diffraction from the surface as well as from the lateral surface of an Si single-crystal strip which is deformed in cantilever bending as a function of the tip displacement. The interference fringes are observed only when the bending strain is applied. Both interference fringes change conspicuously by increasing the bending strain. The number of the interference fringes changes, and the positions and heights of the peaks in the fringes change. These variations can be explained by the change of the interference between the beams in multiple Bragg-Laue modes and those of mirage diffraction based on the dynamical theory of diffraction.

Curie temperature of Nd0.7(Ca, Sr, Ba)0.3MnO3, as determined by electron-spin resonance

A paramagnetic–ferromagnetic transition has been observed in detail by electron-spin resonance (ESR) around the Curie temperature in a series of Nd0.7(Ca, Sr, Ba)0.3MnO3 with a fixed A-site mean radius 〈rA〉=1.21 A. As A-site cation disorder σ2 increases, the ESR linewidth increases and the activation energy obtained from the ESR decreases, suggesting an increase of the local lattice distortions and a weakening of the ferromagnetic correlations with increasing σ2. ESR signals reveal that the A-site cation disorder causes the local microscopic inhomogeneity of the Mn oxidation state, which leads to the broad paramagnetic–ferromagnetic transition.

Determination of anomalous scattering factors from X-ray resonant-scattering-induced Pendellösung fringes: Ge

A new type of Pendellosung fringe, which is induced by X-ray resonant scattering, is measured for several reflections of Ge. This is an extension of a previous study on the GaAs 600 reflection near the Ga K-absorption edge. The energy resolution is much improved, especially by use of synchrotron radiation. The measured profiles of the fringe agree well with the theoretical ones, which in turn makes it possible to determine the anomalous scattering factors f′ from the fringes near the absorption edge. The obtained f′ values are in good agreement with reported theoretical ones.

Change of lattice distortion images in X-ray topography with resonant scattering in the Laue case

Plane-wave topographs of X-rays for the GaAs 200 reflection were recorded using synchrotron radiation near the K-absorption edges of Ga and As. The topographic contrasts caused by lattice defects were changed by tuning the X-ray energy to four typical resonant scattering conditions. A sharp image of a lattice defect was observed when the Borrmann effect disappeared. When the Borrmann effect was conspicuous, an image of lattice distortion around a dislocation was observed, and its contrast was reversed by changing the phase factor of the resonant scattering. The lattice distortion image and its contrast reversal are discussed based on the resonant scattering dynamical theory by introducing the edge-dislocation model. The results show that topographs using resonant scattering should be a new characteristic method in synchrotron topography.