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塩見 雄毅*; Lustikova, J.*; 渡辺 真悟*; 廣部 大地*; 高橋 三郎*; 齊藤 英治
Nature Physics, 15(1), p.22 - 26, 2018/10
被引用回数：17 パーセンタイル：74.55(Physics, Multidisciplinary)Various spintronic phenomena originate from the exchange of angular momentum between the spin of electrons and other degrees of freedom in crystalline materials. Many degrees of freedom, such as magnetization and mechanical motion, have already been united into this exchange framework. However, the nuclear spin -a key angular momentum- has yet to be incorporated. Here we observe spin pumping from nuclear magnetic resonance (NMR), in which nuclear spin dynamics emits a spin current, a flow of spin angular momentum of electrons. By using the canted antiferromagnet MnCO
, in which typical nuclear spin-wave formation is established due to the reinforced hyperfine coupling, we find that a spin current is generated from an NMR. Nuclear spins are indispensable for quantum information technology and are also frequently used in various sensors, such as in magnetic resonance imaging. The observed NMR spin pumping allows spin-current generation from nuclei and will enable spintronic detection of nuclear spin states.
渡辺 真悟*; 廣部 大地*; 塩見 雄毅*; 井口 亮*; 大門 俊介*; 亀田 麻衣*; 高橋 三郎*; 齊藤 英治
Scientific Reports (Internet), 7, p.4576_1 - 4576_6, 2017/07
被引用回数：6 パーセンタイル：29.59(Multidisciplinary Sciences)Spin pumping enables the generation of d.c. and gigahertz-band (GHz-band) voltages from an applied microwave via magnetization dynamics when combined with inverse spin Hall effects. However, generating such voltages in the in-between frequency region, or the megahertz (MHz) band, has been difficult since ferromagnetic resonance usually occurs in the GHz band. Here we show that in spite of GHz-band microwaves applied, MHz-band voltages can be generated by spin pumping with use of nonlinear magnetization dynamics in YFe
O
. The mechanism is ascribed to the MHz-band oscillation of the amplitude of the magnetization precession, which is projected onto a rectified voltage component via spin pumping. The present finding could be useful for frequency down-conversion thanks to the simple and durable structure, continuous-wave operation, and the tunability of an output frequency with low magnetic fields.
田中 真悟*; 横田 秀晴; 大野 宏和; 中山 雅; 藤田 朝雄; 瀧谷 啓晃*; 渡辺 直子*; 小崎 完*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05
In-situ dipole tracer migration tests were conducted at the G.L.-250 m gallery of the Horonobe URL. Laboratory experiments were also conducted to determine the apparent diffusivity (
) and sorption coefficients (
) of cesium and water (HTO) in the rock taken at the gallery to evaluate the performance of Wakkanai formation as natural barrier. The breakthrough curves of non-sorbing tracer (Uranine) obtained at the in-situ dipole tracer migration tests were well described by a dual-channel model in which one-dimensional advection dispersion was taken in account. This suggests that the tracers migrate through at least two different pathways in the fracture. The breakthrough curves also indicated that the peak concentration of the sorbing tracer (cesium) was much smaller than that of the non-sorbing tracer (Uranine), suggesting that the Wakkanai Formation has a high sorptive and low diffusive properties for cesium. The value obtained for cesium was about 3E-12 m
/s, which is significantly smaller than that of water (3E-10 m/s), and the value of cesium was determined to be about 5E-2 ml/g.
田中 真悟; 佐藤 治夫; 大熊 成地*; 渡辺 直子*; 小崎 完*; 佐藤 正知*; 阿部 寛信; 新里 忠史; 青木 和弘
no journal, ,
東京電力福島第一原子力発電所の事故により環境中へ放出された放射性物質の土壌中深度方向の分布状態等について、事故発生から約3か月後に行った1次調査に引き続き、同地点にて、約1年後の2012年2月下旬から3月上旬に掛けて2回目の調査(2次調査)を実施した。収着分配係数(Kd)は、長期的な核種移行予測の際に重要なパラメータの1つである。1次調査において、採取した土壌に対してバッチ法により取得したCsのKdは、1,000(ml/g)以上であり、IのKdは0.4から150(ml/g)の範囲内であった。得られたKdは土壌ごとにばらつきが見られ、Iについては土壌の色と関連があり有機物(腐植)の影響が示唆された。一方でCsのKdについて議論するためには、実験条件の最適化や鉱物分析などの土壌特性評価が必要であり、さらにCsの長期的移行を考える際には、収着の可逆性が重要であることが指摘された。そこで本報では、採取した土壌に対して水簸分級を行い、分級前後の試料において、XRDによる鉱物分析、CEC及びAECの測定、並びにCs及びIの収着・脱着試験を行った結果について報告する。
