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Journal Articles

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite; $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance studies

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ueda, Hiroaki*; Tanioku, Yasuaki*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Takao, Kenta*; Shimoda, Aiko*; et al.

Physical Review B, 98(6), p.064403_1 - 064403_10, 2018/08

 Times Cited Count:6 Percentile:45.58(Materials Science, Multidisciplinary)

To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite, $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. To a considerable degree, the charge compensation between La$$^{3+}$$ and Co$$^{2+}$$ works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin $$4f_1$$ sites at the center of the oxygen tetrahedra, with the $$S$$ = 3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co$$^{2+}$$ ($$S$$ = 3/2, $$L$$ = 1) ions with unquenched orbital moments would be distributed to the other octahedral $$12k$$, $$2a$$, and $$4f_2$$ sites.

Journal Articles

Characterization of epitaxial transformation phenomena induced by the interaction of implanted N-ions with Ti thin films

Kasukabe, Yoshitaka*; Shimoda, Hiroyuki*; Chen, Y.*; Yamamoto, Shunya; Yoshikawa, Masahito; Fujino, Yutaka*

Nuclear Instruments and Methods in Physics Research B, 315, p.131 - 135, 2013/11

 Times Cited Count:1 Percentile:12.7(Instruments & Instrumentation)

Epitaxial transformation phenomena of titanium films due to Nitrogen-implantation have been clarified through in-situ observations by using transmission electron microscope(TEM)and electron energy loss spectroscope (EELS), along with molecular orbital calculations. The N$$^{2+}$$ ions with 62 keV are implanted into as-deposited Ti films which consist of hcp-Ti and TiH$$_{rm x}$$ with preferred orientations, in the 400 kV analytic high resolution TEM combined with ion accelerators at JAEA Takasaki. The result of EELS measurements indicates that the hcp-fcc transformation occurs preferentially above a critical concentration ratio, N/Ti $$sim$$ 0.25. This means that above the N/Ti $$sim$$ 0.25, the invasion of implanted N atom to the N-unoccupied octahedral site in the neighboring unit cell next to the N-occupied one in hcp-Ti occurs preferentially, and induces the growth of nucleus of the hcp-fcc transformation.

JAEA Reports

Measurement of sorption, diffusion and pore physicality for granite sample

Kunimaru, Takanori; Morikawa, Keita; Tachi, Yukio; Kuno, Yoshio*; Hosoya, Shinichi*; Shimoda, Satoko*; Kato, Hiroyasu*; Nakazawa, Toshiyuki*; Ikuse, Hiroyuki*; Kubota, Masako*

JAEA-Data/Code 2012-013, 96 Pages, 2012/07

JAEA-Data-Code-2012-013.pdf:7.41MB
JAEA-Data-Code-2012-013(errata).pdf:0.13MB

For the purpose to understand the relationship between characteristic of mass transport and characteristic of fracture, the following experiments were carried out using core sample, which was sampled from the -300 m Stage. This paper compiled the results of these experiment. (1) Diffusion experiments of Cs, Sr, I and uranin in granite samples (2) Sorption experiments of Cs and Sr on crushed granite (3) Measurement of pore physicality by Mercury Intrusion and water saturation

Oral presentation

Conceptual design study of small-sized high temperature gas-cooled reactor for developing countries, 5; Design of vessel cooling system and steam generator

Mori, Yuichiro*; Maekawa, Isamu*; Shimoda, Sadayuki*; Sato, Hiroyuki; Nomoto, Yasunobu; Ohashi, Hirofumi; Tachibana, Yukio

no journal, , 

no abstracts in English

Oral presentation

Evaluation of concrete waste generated by Fukushima Dai-ichi Nuclear accident, 1; Diffusion and sorption behavior of radionuclides in concrete

Akagi, Yosuke*; Shimoda, Satoko*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

no journal, , 

The Fukushima Dai-ichi Nuclear Power Plant accident has resulted in a large amount of radioactively contaminated concrete. As fundamental basis for developing the treatment and disposal concept for these wastes, migration behavior of radionuclides in concrete was investigated. Sorption and diffusion characteristics of tritiated water, cesium, iodine and uranium were measured at various conditions (concrete types, salinity, etc.).

Oral presentation

Evaluation of concrete waste generated by Fukushima Dai-ichi Nuclear accident, 2; Decontamination of radioactive concrete waste using pulsed power discharge

Sakamoto, Hiroyuki*; Shimoda, Satoko*; Yamada, Kazuo*; Namihira, Takao*; Shigeishi, Mitsuhiro*; Tachi, Yukio

no journal, , 

The Fukushima Dai-ichi Nuclear Plant accident has resulted in a large amount of radioactively contaminated concrete. The possible application of the pulsed power discharge to reduce the amount of contaminated concrete debris as radioactive waste was investigated. This method could decontaminate and reduce the contaminated concrete wastes by separating contaminated matrix from uncontaminated coarse aggregate under pulsed power discharge process.

Oral presentation

$$^{57}$$Fe NMR study in La-Co substituted M-type Sr ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

Zero field NMR experiments on SrFe$$_{12}$$O$$_{19}$$ and Sr$$_{1-x}$$La$$_{x}$$Fe$$_{12-x}$$Co$$_{x}$$O$$_{19}$$ have been performed. The substitued Co sites will be discussed based on the NMR spectra.

Oral presentation

$$^{59}$$Co NMR study in La-Co substituted $$M$$-type Sr Ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

Zero field NMR experiments have been done using powdered samples and single crystals of SrFe$$_{12}$$O$$_{19}$$ and La-Co co-substituted Sr$$_{1-x}$$La$$_x$$Fe$$_{12-x}$$Co$$_{x}$$O$$_{19}$$. The single crystals were grown by the flux method. $$^{59}$$Co NMR signals have been observed in the lower frequency range of 50-100 MHz and in the higher frequency range of 300-400 MHz. Spectral intensity in the lower frequency range is stronger than that in the higher frequency range. We will discuss the spin and charge states of Co ions using the NMR results, some complementary experiments and theoretical considerations.

Oral presentation

NMR study in La-Co substituted M-type Sr Ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

$$^{57}$$Fe and $$^{59}$$Co NMR spectra have been observed for La-Co co-substituted M-type Ferrite. We will microscopically discuss about the Co sites in the co-substituted M-type Ferrite as well as spin and charge states of Co ions.

Oral presentation

$$^{57}$$Fe, $$^{59}$$Co-NMR study in La-Co substituted M-type Sr ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

We will discuss about the Co sites and the electronic states of Co ions in La-Co co-substituted SrFe$$_{12}$$O$$_{19}$$ using the $$^{57}$$Fe and $$^{59}$$Co NMR results.

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