Hide Yoshioka

Effect of Inelastic Waves on Electron Diffraction

The effect of inelastic scattering on electron diffraction by crystals is theoretically studied. It is proved that the effect of inelastic scattering gives rise to an additional complex term to Fourier coefficient of the inner potential. The imaginary part of the additional term explains qualitatively the observation that two components of a doubly refracted electron beam are subjected to different degrees of absorption (Honjo and Mihama, J. Phys. Soc. Japan 9 (1954) 184). The real part of the additional term gives a correction of about 6∼7 % to the calculated value of mean inner potential at accelerating voltages of 30∼40 kv. This explains the systematic difference between the mean inner potential experimentally obtained by electron diffraction and that calculated by the use of diamagnetic susceptibility (Miyake, Proc. Physico-Math. Soc. Japan 22 (1940) 666).

The ESR Study of Growth and Decay Processes of Self-Trapped Holes in AgCl Crystals Doped with Cu

The effects of irradiation on AgCl crystals doped with Cu 2+ ion are studied by the electron spin resonance. A hole released from the Cu 2+ site by irradiation with blue light is self-trapped at an Ag + ion site forming an Ag 2+ center. The Ag 2+ center decays by irradiation with infrared light and the Cu 2+ center is reformed. Reorientation of the symmetry axis of the Ag 2+ center by irradiation with polarized IR light is remarkably observed. The result of the analysis shows that the IR absorption band of the Ag 2+ center is composed of two components and the oscillator strength of the predominant component is about 4 times larger than that of the other, where the former and the latter correspond to the absorption of light polarized perpendicular and parallel to the axis of the Jahn-Teller distortion, respectively. The optical transition process is discussed using a model of the tetragonally distorted (AgCl 6 ) -4 molecule.

Resonance Frequencies of Antiferromagnets Having Antisymmetric Exchange Interaction

The equilibrium positions of sublattice magnetizations and the resonance frequencies of the antiferromagnet having the Dzyaloshinsky-Moriya vector parallel with the easy axis are calculated for arbitrary directions of the applied field. The effect of the parallel susceptibility has been taken into account in the calculation. The results are compared with the experiments on KMnF 3 in the intermediate temperature range. Good agreement is obtained, supporting that the crystal has the Dzyaloshinsky-Moriya vector parallel with the easy axis.

Upper and Lower Critical Fields of TaS2(Pyridine)1/2

The temperature dependences of the upper critical fields, H c2//,⊥ , and the lower critical field, H c1// , have been measured on the single crystal of the layer structure TaS 2 intercalated with p...

Jahn-Teller Effect in the ESR Spectrum of the Complex (AgBr6)4- in Mixed Crystals AgBr1-xClx

Electron spin resonance study shows that holes in AgBr 1- x Cl x ( x =0.85 and 0.7) mixed crystals can be self-trapped as the complexes (AgBr 6 ) 4- . The spectrum of (AgBr 6 ) 4- is associated with the static Jahn-Teller effect. The g values, however, have small anisotropy ( g // =2.078, g ⊥ =2.065). The spectra disappeared above ∼60 K and ∼35 K in AgBr 0.15 Cl 0.85 and AgBr 0.3 Cl 0.7 crystals, respectively.

ESR Investigations of Self-Trapped Holes in Mixed Crystals AgBr1-xClx

New Ag 2+ centers of self-trapped holes were observed in mixed crystals AgBr 1- x C1 x at helium temperatures. Holes are self-trapped at Ag ion site which has a Br ion or two Br ions on its nearest neighbour sites, and form complexes,(AgBrCl 5 ) 4- and (AgBr 2 Cl 4 ) 4- .

Optically Detected Magnetic Resonance of Self-Trapped Excitons in AgBrxCl1-x. Transition from Self-Trapped to Free Exciton

ODMR of self-trapped excitons in mixed crystals AgBr x Cl 1- x (\(0{\lesssim}x{\lesssim}0.53\)) has been studied. With the increase of x , excitons become trapped at Ag sites having increasing numbers of Br ions in their coordination shells. For \(0.3{\lesssim}x{\lesssim}0.53\), excitons seem to be characterized as (AgBr 6 ) 5- complexes. These observations are explained by tunneling of excitons to energetically lower sites. Tunneling is, also, capable of explaining the abrupt change of the self-trapped state to the free state of excitons around x ∼0.55 reported by Kanzaki et al.

On the Electron Diffraction by Flux Lines

A theory of electron-diffraction at magnetic flux lines is presented. For a flux line with an infinitesimal radius, a good approximation to Aharonov and Bohms results is obtained by the use of Kirchhoffs diffraction theory. Then, diffraction in a crystal having a flux line with a finite radius is treated by the method of eikonal functions similar to that used in Katos diffraction theory for imperfect crystals. The trajectory of the electron which is derived from Fermats principle has properties familiar in solid state physics. The possibilities of observing flux lines in type-II superconductors are discussed.

ODMR of Self-Trapped Excitons in AgCl Crystals: Analysis of Polarization and Intensity of ODMR

A phenomenological theory of the radiative decay of the self-trapped excitons (STE) in AgCl crystals at low temperatures is developed. The radiative decay of magnetic sublevels of the triplet STE is determined by singlet odd wave functions admixed into the lowest triplet wave functions by spin-orbit interaction and lattice vibrations. At 4.2 K, the transition probabilities between the triplet and the singlet states of the STE through the direct process of the spin-lattice relaxation turn out to be much larger than the corresponding probabilities between the sublevels of the triplet. The theory explains satisfactorily the ODMR signals observed at 4.2 K with the assumption of negative sign of zero-field splitting, D . Discrepancies found for signals of the STE at 1.6 K are discussed in terms of the polarization of the STE produced by the neighboring electron center.

Orientation of Pyridine in TaS2(Py)1/2

X-ray diffraction measurements on TaS 2 (Py) 1/2 single crystals of the single phase with the layer spacing 12.03 A showed that the intercalated pyridine molecules lay with aromatic ring planes perpendicular to the TaS 2 layers, and the nitrogen atom located midway between the TaS 2 layers with the long C–N axis parallel to the layers.