Optical study on the doping and temperature dependence of the anisotropic electronic structure in bilayered manganites:La2−2xSr1+2xMn2O7(0.3<~x<~0.5)

Abstract The temperature dependence of the pure nuclear quadrupole resonance of 35Cl and 37Cl in solid CHCl2COOH and CDCl2COOD has been measured. The spectra are doublets according to two different sites, Cl (I) and Cl (II), of the chlorine atoms in the CXCl2 group (X = H,D). In CHCl2COOH and CDCl2COOD the 37Cl spectra became unobservable above 198 K and 175 K and the 35Cl spectra vanished at 238 K and 226 K, respectively. The temperature dependence was calculated using the Bayer-Kushida theory which gives a satisfactory approach in the case of the compounds investigated here. A small difference has been found in the temperature dependence of the resonance frequen cies for CI (I) and CI (II) in both the CHCl2 and CDCl2 group, which is probably due to differences in the bond lengths of CI (I) and CI (II). Furthermore, there is a different temperature dependence of the resonance frequencies of the chlorine isotopes at the sites CI (I) and CI (II). This gives evi dence for the so-called isotope effect: i. e. there are slightly different thermal motions for the chlorine isotopes which are involved in the averaging of the electric field gradient tensor. The re placement of protons by deuterons gave a shift of the resonance frequencies of about 20 kHz to lower values. This may be primarily caused by effects of deuteration on the electronic structure.

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Optical Study of Electronic Structure and Photoinduced Dynamics in the Organic Alloy System [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6

Applied Sciences ◽

10.3390/app9061174 ◽

2019 ◽

Vol 9 (6) ◽

pp. 1174 ◽

Cited By ~ 1

Author(s):

Tadahiko Ishikawa ◽

Yohei Urasawa ◽

Taiki Shindo ◽

Yoichi Okimoto ◽

Shin-ya Koshihara ◽

...

Keyword(s):

Phase Transition ◽

Electronic Structure ◽

Absorption Spectra ◽

Structural Changes ◽

Alloy System ◽

Charge Ordering ◽

Center Frequency ◽

Relaxation Processes ◽

Optical Study ◽

Small Shift

Over the past two decades (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene), which exhibits a metal–insulator (M–I) phase transition with charge–ordering (CO), has been investigated energetically because of attractive characteristics that include ultrafast and massive photoinduced spectral and structural changes. In contrast, while its crystal structure has much in common with the (EDO-TTF)2PF6 crystal, the organic alloy system of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 (MeEDO-TTF = 4,5-ethylenedioxy-4′-methyltetrathiafulvalene) exhibits a quite different type of M–I phase transition that is attributed to Peierls instability. Here, an optical study of the static absorption spectra and the time-resolved changes in the absorption spectra of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 are reported. The observed absorption spectra related to the electronic structure are highly anisotropic. With a reduction in temperature (T), the opening of a small optical gap and a small shift in the center frequency of the C=C stretching mode are observed along with the M–I phase transition. Additionally, photoinduced transient states have been assigned based on their relaxation processes and transient intramolecular vibrational spectra. Reflecting small valence and structural changes and weak donor–anion interactions, a photoinduced transient state that is similar to the thermal-equilibrium high-T metallic phase appears more rapidly in the alloy system than that in (EDO-TTF)2PF6.

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The electronic structure of ilvaite and the pressure and temperature dependence of its 57Fe Mössbauer spectrum

Solid State Communications ◽

10.1016/0038-1098(80)91128-x ◽

1980 ◽

Vol 34 (12) ◽

pp. iv

Author(s):

B.J. Evans

Keyword(s):

Electronic Structure ◽

Temperature Dependence ◽

Mossbauer Spectrum ◽

Mössbauer Spectrum ◽

57Fe Mössbauer

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Optical Study of Electronic Structure and Nonmetal-Metal Transition of Gd2S3

Journal of the Physical Society of Japan ◽

10.1143/jpsj.62.4331 ◽

1993 ◽

Vol 62 (12) ◽

pp. 4331-4337 ◽

Cited By ~ 8

Author(s):

Shin-ichi Kimura ◽

Fumitaka Arai ◽

Takashi Suzuki ◽

Mikihiko Ikezawa

Keyword(s):

Electronic Structure ◽

Optical Study

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ELECTRONIC STRUCTURE AND CONDUCTIVITY OF HYDROCARBON FILMS OBTAINED IN PLASMA DISCHARGES OF TOKAMAK T-10

IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA ◽

10.6060/ivkkt.20186111.1y ◽

1970 ◽

Vol 61 (11) ◽

Author(s):

Galina A. Sokolina ◽

Igor I. Arkhipov ◽

Nikolay Yu. Svechnikov ◽

Sergey A. Grashin

Keyword(s):

Activation Energy ◽

Electronic Structure ◽

Temperature Dependence ◽

Direct Current ◽

Plasma Discharges ◽

X Ray ◽

Hydrocarbon Films ◽

Direct Current Conductivity ◽

Current Voltage ◽

Current Voltage Characteristics

Amorphous hydrocarbon films on silicon substrates obtained in the chamber of tokamak T-10 with space-bounded deuterium plasma by carbon diaphragms were studied. Using the methods of spectrophotometry, ellipsometry, X-ray photoemission spectroscopy and X-ray excited Auger electron spectroscopy, it was established that the refraction and absorption coefficients of films, as well as the parameters of the electronic structure such as the magnitude of the band gap, the fraction of sp2-hybridized carbon and the chemical composition of impurities depend on the characteristics of the discharge in the tokamak. It is shown that the deposited films refer to high-resistance dielectrics, and they can be classified by optical properties as hard or soft amorphous hydrocarbon films, depending on the type of the plasma discharge (pulse working discharge or long-term low-energy cleaning discharge). Wherein, the conductivity of hard films is less than that of soft films, which corresponds to a smaller fraction of sp2-states of carbon in these films and to a higher value of the band gap. The current-voltage characteristics and the temperature dependence of the direct current conductivity of hard and soft films were measured. It was shown that in the temperature range of 293–550 K, the conductivity is determined by the hopping conductivity mechanism over localized states near the Fermi level and the boundaries of the allowed bands. The hopping conductivity mechanism is also indicated by the power law obtained at room temperature at alternating current with a value of a power exponent close to 0.8. The measurement of the current-voltage characteristics and the temperature dependence of the conductivity of hard and soft films showed a significant difference in the activation energy of conductivity and the conductivity at an elevated temperature. The established dependences of the direct current conductivity and the activation energy value of the films on the discharge parameters can be used as diagnostic benchmarks of different types of plasma discharges in a tokamak. Data on the electrical conductivity of the films are analyzed within the framework of the concept of the electronic structure of amorphous non-crystalline materials.

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