[en] An ⁵⁷Fe Moessbauer spectroscopic study of iron-based layered superconductors La_0.87Ca_0.13FePO and LaFeAsO_0.93F_0.07 under external magnetic fields of up to 14T was performed. Our results suggest that hyperfine fields induced by local magnetic moments are, if any, small and that the magnetic feature of Fe in La_0.87Ca_0.13FePO and LaFeAsO_0.93F_0.07 is most likely to be paramagnetism with itinerant electrons. This feature is confirmed both above and below the transition temperature for LaFeAsO_0.93F_0.07. Furthermore, the temperature dependence of the iron-specific phonon density of states in La_0.87Ca_0.13-FePO was measured by using the nuclear resonant inelastic scattering of synchrotron radiation. We have found that the temperature-dependent change in the iron-specific phonon density of states of La_0.87Ca_0.13FePO was smaller than that of LaFeAsO_0.89F_0.11. (author)

[en] The mixed valence compounds which take position at the border of metals and nonmetals are the group of the matters which possess the possibility of important but undeveloped phenomena, for example, the competition of negative U center state, metallic state and the superconductive state due to the condensation of bipolaron is expected. The authors paid attention to three-dimensional halogen-bridged mixed valence complex Cs₂Au₂X₆, and have carried out the systematic studies on its structure and electronic condition. The ¹⁹⁷Au Moessbauer spectrometry has been carried out for Cs₂Au₂X₆ at Research Reactor Institute, Kyoto University, and the detailed knowledge was able to be obtained on the Au mixed valence state. Also the experiment of ¹²⁹I Moessbauer spectrometry can be performed for Cs₂Au₂I₆, which gives the quantitative information on the charge of bridging I and the chemical bond of Au-I. The preparation of the specimen Cs₂Au₂I₆ and ¹²⁹Te radiation source, the measurement of Moessbauer spectra, and the experimental results are reported. The ¹²⁹I Moessbauer spectrum is shown, and it is known that two kinds of iodine states existed. (K.I.)

[en] Fluoroaluminum phthalocyanine (AlPcF) is the compound that has the one-dimensional chain structure, in which flat plate phthalocyanine complex makes a laminate, and it has been known that by doping it with an electron receptor like iodine, its electric conductivity increases. As for the form and electronic condition of doped iodine, its charge transfer and the interaction of iodine and AlPcF are not well known. The ESR signal observed in doped AlPcF disappears at low temperature, and the possibility that antiferromagnetic transition occurs is suggested, but it is not clear. ¹²⁹I was doped in AlPcF, and its Moessbauer effect was measured, in this way, the chemical form and electronic condition of the iodine in AlPcF, and the relation of antiferromagnetic transition with the iodine concentration were studied. The AlPcF sample, the method of iodine doping, the X-band ESR measurement for antiferromagnetic transition, and the measurement of ¹²⁹I Moessbauer effect are reported. The moessbauer spectra of the ¹²⁹I doped AlPcF are shown, and two kinds of iodine states were confirmed in the spectrum for lowest iodine concentration. Also the Moessbauer parameters as shown. It was found that I₃^- took part deeply in the antiferromagnetic transition of AlPcF. (K.I.)

[en] Anisotropic phonon modes of stage-1 FeCl₃-graphite intercalation compounds were studied by inelastic nuclear resonant scattering. Partial phonon modes concerning Fe atoms were measured with incident x-rays either parallel or perpendicular to graphite layers. The observed spectra well show the character of the phonon density of state weighted by the projection of phonon polarization vector to the incident x-ray. (author)

No abstract available

[en] This study examined the magnetic structure of 11 types of iron-based superconductor base material FeTe, using Moessbauer spectroscopy under strong magnetic field. The authors observed the Moessbauer spectra and internal magnetic field when applying the magnetic field of 0 T and 8 T at 4.3 K to FeTe_0_._9. The Moessbauer spectra when applying a magnetic field of 0 T and 8 T at 200 K were also shown. FeTe_0_._9 has complex magnetic order at below the magnetic transition temperature of about 70 K, and changes in internal magnetic field distribution was observed with the application of a magnetic field of 8 T, It was found that the size of the antiferromagnetic interaction due to the generation of magnetic order is the size comparable to 8 T. In addition, in the phase without magnetic order at high temperatures, the applied magnetic field and internal magnetic field had almost the same size, which shows that this material has paramagnetic behavior without magnetism. In addition, by the application of the magnetic field asymmetric between left and right of spectrum, the magnetic field changed to nearly symmetric form, which indicated that the correlation between the crystal axis subject to quadrupole splitting and the orientation of magnetic moment hardly existed. (A.O.)

[en] A parent compound of iron-based superconductor, Fe_1.1Te, and a Se-doped superconductor, FeTe_0.5Se_0.5, were investigated using ¹²⁵Te-Mössbauer spectroscopy. By measuring precise temperature dependence of the spectra, discontinuous line broadening in the Fe_1.1Te near the antiferromagnetic transition temperature (T_N) of Fe was observed. While the broadening of the line width were observed in both samples as the temperature decreases, the temperature dependences of the line width were well reproduced as that of the recoilless fraction, assuming the Debye model with a Debye temperature of about 200 K. The discontinuous additional line broadening in the Fe_1.1Te can be considered as the internal magnetic fields of Te below T_N, since the temperature dependence of internal magnetic fields of Te is similar to that of Fe in ⁵⁷Fe-Mössbauer spectroscopy. Therefore, hybridization of the electronic orbital of Te and Fe was suggested and the transferred magnetic moment of Te was induced through the antiferromagnetic order of Fe at T_N.

[en] Iron perovskites CaFeO₃ and La_0.33Sr_0.67FeO₃ show charge disproportionation, resulting in charge-ordered states with 'Fe³⁺': 'Fe⁵⁺ = 1:1 and = 2:1, respectively. We have performed nuclear resonant scattering measurements of photon density of states in CaFeO₃ and La_0.33Sr_0.67FeO₃. With decreasing temperature, we found changes in the phonon density of states in the region of 30-60 meV in CaFeO₃, while only a small change was observed in La_0.33Sr_0.67FeO₃. This finding gives support to the previous finding that the charge disproportionation is driven by electron-photon interaction in CaFeO₃, and electronically in La_0.33Sr_0.67FeO₃. (author)

[en] The first observation of the nuclear resonant scattering from the 37.1-keV level of ¹²¹Sb and the 22.5-keV level of ¹⁴⁹Sm excited by synchrotron radiation is reported. Delayed emission of fluorescent K or L X-rays following the internal conversion process is mainly used to observe this resonance. The evaluated energy of each excited level was 37.147±0.023 keV for ¹²¹Sb and 22.496±0.022 keV for ¹⁴⁹Sm. Each half-life of the excited level was evaluated to be 3.47±0.39 ns for ¹²¹Sb and 7.40±1.15 ns for ¹⁴⁹Sm. These values agree well with the reported values for each level. (author)

No abstract available