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Journal Articles

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

Oba, Yojiro; Adachi, Nozomu*; Todaka, Yoshikazu*; Gilbert, E. P.*; Mamiya, Hiroaki*

Physical Review Research (Internet), 2(3), p.033473_1 - 033473_6, 2020/11

Journal Articles

Characterization of spin superstructures using neutron transmission spectra

Mamiya, Hiroaki*; Oba, Yojiro; Oikawa, Kenichi

Shiki, 39, P. 4, 2018/06

no abstracts in English

Journal Articles

Magnetic Bragg dip and Bragg edge in neutron transmission spectra of typical spin superstructures

Mamiya, Hiroaki*; Oba, Yojiro; Terada, Noriki*; Watanabe, Norimichi*; Hiroi, Kosuke; Shinohara, Takenao; Oikawa, Kenichi

Scientific Reports (Internet), 7(1), p.15516_1 - 15516_8, 2017/11

 Times Cited Count:1 Percentile:8.15(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Nearly localized nature of $$f$$ electrons in Ce$$T$$In$$_5$$ ($$T$$=Rh, Ir)

Fujimori, Shinichi; Okane, Tetsuo; Okamoto, Jun; Mamiya, Kazutoshi; Muramatsu, Yasuji; Fujimori, Atsushi*; Harima, Hisatomo*; Aoki, Dai*; Ikeda, Shugo*; Shishido, Hiroaki*; et al.

Physical Review B, 67(14), p.144507_1 - 144507_5, 2003/04

 Times Cited Count:33 Percentile:79.88(Materials Science, Multidisciplinary)

We have performed angle-resolved photoemission spectroscopy ($$hnu=21.2, 40.8$$~eV) and 3$$d$$-4$$f$$ resonant photoemission spectroscopy ($$hnu sim 881$$~eV) studies on the layered cerium compounds Ce$$T$$In$$_5$$ ($$T$$=Rh and Ir), which show competition between superconductivity and antiferromagnetism. The results suggest that the Ce~4$$f$$ electrons in both compounds are nearly localized. We have found that although the Ce~4$$f$$ electrons in the superconducting CeIrIn$$_5$$ are more delocalized than those in the antiferromagnetic CeRhIn$$_5$$, their electronic structures are very similar to each other.

Oral presentation

A SANS study on perpendicular magnetic recording hard disk media

Hagiya, Hiroyuki; Oku, Takayuki; Kira, Hiroshi; Shinohara, Takenao; Suzuki, Junichi; Takeda, Masayasu; Kakurai, Kazuhisa; Yokoyama, Makoto*; Nishihara, Yoshikazu*; Oba, Yojiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Quantitative evaluation of magnetic cluster size in perpendicular magnetic recording media

Hagiya, Hiroyuki; Oku, Takayuki; Kira, Hiroshi; Shinohara, Takenao; Suzuki, Junichi; Kakurai, Kazuhisa; Yokoyama, Makoto*; Nishihara, Yoshikazu*; Mamiya, Hiroaki*; Oba, Yojiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

In situ experiment for redox buffer capacity with backfill in the subsurface environment

Murakami, Hiroaki; Amano, Yuki; Amamiya, Hiroki; Sasaki, Yoshito; Iwatsuki, Teruki; Yoshikawa, Hideki

no journal, , 

no abstracts in English

Oral presentation

Planktonic and attached microbes in deep subsurface

Sasaki, Yoshito; Asano, Takahiro*; Ise, Kotaro; Sato, Tomofumi; Murakami, Hiroaki; Amamiya, Hiroki; Amano, Yuki; Iwatsuki, Teruki; Yoshikawa, Hideki

no journal, , 

no abstracts in English

Oral presentation

Neutron diffraction study of rare-earth compound Ho$$_5$$Pd$$_2$$ with a large magnetocaloric effect

Kitazawa, Hideaki*; Kawamura, Yukihiko*; Terada, Noriki*; Mamiya, Hiroaki*; Suzuki, Hiroyuki*; Doenni, A.*; Kaneko, Koji; Metoki, Naoto; Igawa, Naoki

no journal, , 

We have performed neutron powder diffraction experiments at JRR-3 using polycrystalline Ho$$_5$$Pd$$_2$$. The magnetic peaks with a propagation vector k = (0.18, 0.18, 0.18) are gradually developing below about 100 K. The peak width is significantly broader than an experimental resolution even temperature is 5 K. These results indicate that Ho$$_5$$Pd$$_2$$ is a short-range ordered antiferromagnet with a long wave length.

Oral presentation

Neutron scattering study toward to development of energy-efficient environment-friendly refrigeration technology

Kitazawa, Hideaki*; Kawamura, Yukihiko*; Mamiya, Hiroaki*; Terada, Noriki*; Suzuki, Hiroyuki*; Tsujii, Naohito*; Doenni, A.*; Kaneko, Koji; Metoki, Naoto; Igawa, Naoki; et al.

no journal, , 

In this paper, we will demonstrate some application of neutron scattering for magnetic refrigerant materials Ho$$_5$$Pd$$_2$$ and dilute spinel ferrites. In order to determine the magnetic structure, we have performed neutron powder diffraction experiments at JRR-3. The magnetic peaks with a propagation vector k = (0.18, 0.18, 0.18) are gradually developing. The peak width is significantly broader even 5 K, indicating a short-range order with a long wave length.

Oral presentation

Interaction of rare earth elements and suspended matters contained in Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Sasaki, Takayuki*; Sato, Nobuaki*

no journal, , 

For understanding of the migration behavior of minor actinides (MA) in groundwater, the interaction of rare earth elements and suspended matters contained in Horonobe deep groundwater was studied. From this chemical analog study, it is suggested that the migration behavior of MA in the Horonobe groundwater system seems to be regulated by the formation of phosphate precipitation and small percentage of MA would be carried in the groundwater as pseudo colloids like MA-humic substance complex.

Oral presentation

Investigation for colloids in the groundwater of Horonobe URL, 1; Characterization of colloids in the groundwater by using ultra filtration

Amano, Yuki; Amamiya, Hiroki; Murakami, Hiroaki; Iwatsuki, Teruki; Terashima, Motoki; Mizuno, Takashi; Kirishima, Akira*; Kuno, Atsushi*; Sasaki, Takayuki*; Kubota, Takumi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on colloids in the groundwater of Horonobe URL, 3; Interaction of rare earth elements and suspended matters contained in Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Sasaki, Takayuki*; Sato, Nobuaki*

no journal, , 

no abstracts in English

Oral presentation

Study on colloids in the groundwater of Horonobe URL, 2; Quantitative analysis of U, Th and rare earth elements in Horonobe deep groundwater

Kokami, Takayuki*; Sasaki, Takayuki*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Kirishima, Akira*

no journal, , 

no abstracts in English

Oral presentation

Giant magnetocaloric effect and short-range ordering of magnetic refrigerant materials R$$_5$$Pd$$_2$$(R=Tb, Ho)

Kitazawa, Hideaki*; Kawamura, Yukihiko*; Keller, L.*; Toyoizumi, Saori*; Terada, Noriki*; Suzuki, Hiroyuki*; Mamiya, Hiroaki*; Doenni, A.*; Lee, S.*; Metoki, Naoto; et al.

no journal, , 

Neutron Scattering study has been carried out in order to reveal the magnetic structure of the antiferromagnet Ho$$_5$$Pd$$_2$$, which shows giant magnetocaloric effect. We observed short rage magnetic order at k=0.18, 0.18, 0.18 above the antiferromagnetic transition temperature $$T$$$$_N$$. Tb$$_5$$Pd$$_2$$ also showed magnetic short range correlation above the temperature higher than 2$$times$$$$T$$$$_N$$.

Oral presentation

Estimation of palaeohydrochemical conditions using carbonate minerals

Amamiya, Hiroki; Mizuno, Takashi; Iwatsuki, Teruki; Yuguchi, Takashi; Murakami, Hiroaki; Kokubu, Yoko

no journal, , 

The long-term evolution of geochemical environment in deep underground is indispensable research subject for geological disposal of high-level radioactive waste. Many researchers have made efforts previously to elucidate the geochemical environment within the groundwater residence time based on the analysis of the actual groundwater. However, it is impossible to estimate the geochemical environment for the longer time scale than the groundwater residence time in this method. In this case, analysis of the chemical properties of secondary minerals are one of useful method to estimate the past hydrochemical characteristics (temperature, salinity, pH and redox potential). We reviewed the previous studies on carbonate minerals and geochemical conditions in deep underground and estimated the hydrochemical characteristics of past groundwater by using carbonate minerals in crystalline rock at Tono area, Japan. As a result, it is found that temperature and salinity of the groundwater during crystallization of carbonate minerals were evaluated quantitatively. On the other hand, pH and redox potential can only be understood qualitatively. However, it is suggested that the content of heavy metal elements such as manganese, iron and uranium, and rare earth elements in the carbonate minerals are useful indicators for estimating redox potential.

Oral presentation

Estimation and thermodynamic analysis of natural thorium, uranium, and REE concentrations in groundwater at Horonobe URL

Sasaki, Takayuki*; Kokami, Takayuki*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kobayashi, Taishi*; Kirishima, Akira*

no journal, , 

For thermodynamic analysis of the trace metals in groundwater, concentrations of Th, U, and rare earth elements (REEs) were investigated at Horonobe Underground Research Laboratory. Groundwater was sampled in anaerobic condition directly from a packed section in the boreholes drilled to 140 m and 250 m depth in drift. The colloidal distribution was checked by an on-site batch ultrafiltration unit using 0.2 $$mu$$m or 10 kDa membranes. As the result, both Th and U concentrations could be estimated by thermodynamic calculations, assuming that the soluble solid phases are restricted to ThO$$_{2}$$(cr) and UO$$_{2}$$(cr), respectively. Meanwhile, the concentrations of REEs were also very low, and significant colloidal distribution for lighter REEs was observed. In the thermodynamic analysis where the lanthanide phosphate was assumed to be a solid phase, the experimental plots matched better with the calculated one, even though the changing trend differs from each other.

Oral presentation

Geosphere stability project, 6; Chronological and chemical analyses of carbonate minerals

Watanabe, Takahiro; Kokubu, Yoko; Murakami, Hiroaki; Yokoyama, Tatsunori; Amamiya, Hiroki; Mizuno, Takashi; Kubota, Mitsuru; Iwatsuki, Teruki

no journal, , 

Chronological and geochemical studies of fracture filling calcite in rocks provide the information for changes in geochemical condition, such as redox potential and pH in geological environments. Because the calcite can be found as common filling minerals in the natural samples, age zoning and spatial distribution of chemical composition in the calcite could be a wide-use indicator to reconstruct the past environmental changes. Radiometric (U-Pb) dating in a micro scale area (less than 10 micrometer) on the filling mineral surface by laser ablation-inductively coupled plasm mass spectrometry system (LA-ICPMS) has been applied to geological samples. Additionally, past redox potential has been estimated by Fe contents in the carbonates, which is based on the distribution coefficient of Fe between calcite deposit and groundwater. In this study, we evaluated the possibility of in-situ radiometric dating for the filling minerals by LA-ICPMS and redox potential reconstruction by the theoretical calculation using the distribution coefficient.

Oral presentation

Anomalous magnetic nanostructure induced by HPT straining

Oba, Yojiro; Adachi, Nozomu*; Todaka, Yoshikazu*; Mamiya, Hiroaki*

no journal, , 

no abstracts in English

Oral presentation

Spin structural analyses using magnetic Bragg dips and edges

Mamiya, Hiroaki*; Oba, Yojiro; Terada, Noriki*; Watanabe, Norimichi*; Hiroi, Kosuke; Shinohara, Takenao; Oikawa, Kenichi

no journal, , 

no abstracts in English

24 (Records 1-20 displayed on this page)