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Magnetic hysteresis induction with nanocolumnar defects in magnetic insulators

針井 一哉*; 埋田 真樹; 有沢 洋希*; 日置 友智*; 佐藤 奈々; 岡安 悟; 家田 淳一

Journal of the Physical Society of Japan, 92(7), p.073701_1 - 073701_4, 2023/07

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Magnetic property modification of an easy-plane magnetic insulator caused by an accumulation of nanocolumnar defects along the film normal was investigated by numerical simulations and heavy-ion beam irradiation experiments. Micromagnetic simulations suggest that depending on the density of the nonmagnetic nanocolumnar defects, the microstructure of the fragmented ferromagnetic domains is formed leading to magnetic coercivity enhancement as well as magnetization reduction. To prove this prediction, gold ions with 300 MeV were used for the irradiation to create amorphous nanocolumnar defects in crystalline bismuth-doped lutetium iron garnet (Bi:LuIG) films. As increasing the ion-irradiation dose, the modifications of the saturation magnetization and magnetic coercivity were observed in an uncorrelated manner; the enhancement of magnetic coercivity exhibits a fluence threshold whereas the decrease of saturation magnetization caused by ion-beam damage is monotonic with increasing beam fluence. These behaviors qualitatively agree with the numerical simulations and the models by continuum percolation theory. Because the irradiation effects are controlled by beam fluences, the present method has the potential to be a microstructuring technique for magnetic insulator.


Temperature-variable apparatus for measuring Barnett field

埋田 真樹; 中堂 博之; 今井 正樹; 佐藤 奈々; 齊藤 英治

Review of Scientific Instruments, 94(6), p.063906_1 - 063906_8, 2023/06

We have developed experimental equipment for observing the Barnett effect, in which mechanical rotation magnetizes an object, at low temperatures. A sample in a rotor is rotated bidirectionally using a temperature-controlled high-pressure gas. The stray field generated from the sample due to the Barnett effect was detected using a fluxgate magnetic sensor with a sensitivity on the order of several picoteslas, even at low temperatures. By replacing the rotor with a solenoid coil, the magnetic susceptibility of the sample was estimated from the stray field to be of the same order of magnitude as that due to the Barnett effect. The Barnett field was estimated using the dipole model. To assess the performance of the setup at low temperatures, measurements were performed on commercial magnetite (Fe$$_3$$O$$_4$$) nanogranules. We confirmed the accordance of the $$it{g'}$$ factor between the experimental results using the present setup and those of our previous study performed at room temperature.


Nonlinear magnon polaritons

Lee, O.*; 山本 慧; 埋田 真樹; Zollitsch, C. W.*; Elyasi, M.*; 吉川 貴史*; 齊藤 英治; Bauer, G. E. W.*; 紅林 秀和*

Physical Review Letters, 130(4), p.046703_1 - 046703_6, 2023/01

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

We experimentally and theoretically demonstrate that nonlinear spin-wave interactions suppress the hybrid magnon-photon quasiparticle or "magnon polariton" in microwave spectra of an yttrium iron garnet film detected by an on-chip split-ring resonator. We observe a strong coupling between the Kittel and microwave cavity modes in terms of an avoided crossing as a function of magnetic fields at low microwave input powers, but a complete closing of the gap at high powers. The experimental results are well explained by a theoretical model including the three-magnon decay of the Kittel magnon into spin waves. The gap closure originates from the saturation of the ferromagnetic resonance above the Suhl instability threshold by a coherent back reaction from the spin waves.


Electric readout of magnetic stripes in insulators

Chen, Y.*; 塩見 雄毅*; Qiu, Z.*; 新関 友彦*; 埋田 真樹*; 齊藤 英治

Scientific Reports (Internet), 9, p.19052_1 - 19052_8, 2019/12

 被引用回数:0 パーセンタイル:0(Multidisciplinary Sciences)

In superconductors, a topological configuration of the superconducting order parameter called a superconducting vortex carries magnetization. Such a magnetic topological object behaves like a minute particle generating a magnetic flux. Since the flux is localized with a nanometer scale, the vortex provides a nano-scale probe for local magnetic fields. Here we show that information of magnetic stripes in insulators can be read out by using vortices in an adjacent superconductor film as a probe. The orientation and width of magnetic micro stripes are both transcribed into resistance change of the superconductor through the modulation of vortex mobility affected by local magnetization. By changing the direction of external magnetic fields, zero-field resistance changes continuously according to the stripe orientation, and its modulation magnitude reaches up to 100%. The width of the stripes can also be estimated from the oscillatory magnetoresistance. Our results demonstrate a new possibility for non-volatile analog memory devices based on topological objects.


C-face interface defects in 4H-SiC MOSFETs studied by electrically detected magnetic resonance

梅田 享英*; 岡本 光央*; 荒井 亮*; 佐藤 嘉洋*; 小杉 亮治*; 原田 信介*; 奥村 元*; 牧野 高紘; 大島 武

Materials Science Forum, 778-780, p.414 - 417, 2014/02

 被引用回数:2 パーセンタイル:73.38

炭化ケイ素(SiC)金属-酸化膜-半導体 電界効果トランジスタ(MOS FET)の界面欠陥を電流検出型磁気共鳴(EDMR)により調べた。SiC MOSFETはカーボン(C)面上に作製し、水蒸気酸化及び800$$^{circ}$$Cでの水素処理、又は、乾燥酸素を用いた二種類の方法によりゲート酸化膜を形成した。乾燥酸素によるゲート酸化膜を有するMOSFETのチャンネル移動度は1cm$$^{2}$$/Vs以下であるが、水素処理ゲート酸化膜を有するMOSFETは90cm$$^{2}$$/Vsである。低温(20K以下)でのEDMR測定の結果、シリコン面上に作製したMOSFETでは観測されないC面特有の欠陥シグナルが検出された。$$gamma$$線照射を行ったところ、このC面特有の欠陥シグナルが大きくなり、それとともにチャンネル移動度が低下することが判明した。これより、水素処理により終端されていたC欠陥が$$gamma$$線照射により離脱し、C面固有の欠陥となること、この欠陥がチャンネル移動度の低下に関与することが推測される。


Negative-U system of carbon vacancy in 4H-SiC

Son, N. T.*; Trinh, X. T.*; L${o}$vile, L. S.*; Svensson, B. G.*; 河原 洸太朗*; 須田 淳*; 木本 恒暢*; 梅田 享英*; 磯谷 順一*; 牧野 高紘; et al.

Physical Review Letters, 109(18), p.187603_1 - 187603_5, 2012/11

 被引用回数:198 パーセンタイル:98.05(Physics, Multidisciplinary)

Nitrogen-doped n-type 4H-Silicon carbide (SiC) epitaxial layers were irradiated with electrons at 250 keV. Carbon vacancy (V$$_{C}$$) signals at both the h and k sites were studied using photoexitation Electron Paramagnetic Resonance (photo-EPR) and Deep Level Transient Spectroscopy (DLTS). As a result, double negative charge states of V$$_{C}$$, showing its negative-U system were revealed. By the direct correlation between EPR and DLTS data, it was concluded that Z$$_{1}$$ is V$$_{C}$$ at h site and Z$$_{2}$$ is V$$_{C}$$ at k site. In addition, we concluded that EH$$_{7}$$ is a single donor level of V$$_{C}$$.



川村 淳; 牧野 仁史; 笹尾 英嗣; 新里 忠史; 安江 健一; 浅森 浩一; 梅田 浩司; 石丸 恒存; 大澤 英昭; 江橋 健; et al.

JAEA-Research 2010-027, 85 Pages, 2010/09




Study on perturbation scenario for uplift and denudation in performance assessment of a HLW disposal system

川村 淳; 安江 健一; 新里 忠史; 常盤 哲也; 江橋 健; 大井 貴夫; 牧野 仁史; 石丸 恒存; 梅田 浩司

Proceedings of 2008 East Asia Forum on Radwaste Management Conference (2008 EAFORM 2nd Conference) (USB Flash Drive), 6 Pages, 2008/10




川村 淳; 大井 貴夫; 新里 忠史; 安江 健一; 常盤 哲也; 丹羽 正和; 島田 耕史; 黒澤 英樹; 浅森 浩一; 河内 進; et al.

JAEA-Research 2008-018, 47 Pages, 2008/03




高レベル放射性廃棄物地層処分にかかわる天然現象影響評価に関する研究計画書; 当面5か年の計画,H18年度版

川村 淳; 大井 貴夫; 牧野 仁史; 梅田 浩司; 新里 忠史; 安江 健一; 河内 進; 石丸 恒存; 瀬尾 俊弘; 蛯名 貴憲*; et al.

JAEA-Review 2006-039, 60 Pages, 2007/01


本計画では、高レベル放射性廃棄物地層処分にかかわる地質環境の長期安定性研究から天然現象影響評価に関する研究を対象として、研究の必要性や反映の意義に基づいた目的と「我が国における高レベル放射性廃棄物地層処分の技術的信頼性; 地層処分研究開発第2次取りまとめ(第2次取りまとめ)」までに実施された研究成果,「高レベル放射性廃棄物の地層処分技術に関する知識基盤の構築(H17レポート)」までになされた研究成果とをまとめて、「研究とこれまでの経緯」として記述するとともに、今後の当面5年程度の計画を「フェーズ2における研究目的」,「研究内容」として記述し、それを実施するために必要となる天然現象に関する知見及び影響評価に必要となる個別現象にかかわる知見等を案としてまとめた。


Study on evaluation method for potential impacts of "Natural Phenomena" on a HLW disposal system

川村 淳; 大井 貴夫; 牧野 仁史; 梅田 浩司; 新里 忠史; 石丸 恒存; 瀬尾 俊弘

Proceedings of 2006 East Asia Forum on Radwaste Management Conference (2006 EAFORM Conference), p.350 - 367, 2006/11




藤根 幸雄; 村田 幹生; 阿部 仁; 高田 準一; 塚本 導雄; 宮田 定次郎*; 井田 正明*; 渡辺 眞樹男; 内山 軍蔵; 朝倉 俊英; et al.

JAERI-Research 99-056, p.278 - 0, 1999/09





川村 淳; 牧野 仁史; 大井 貴夫; 梅田 浩司; 新里 忠史; 石丸 恒存

no journal, , 




川村 淳; 牧野 仁史; 梅田 浩司; 大井 貴夫; 新里 忠史; 石丸 恒存

no journal, , 




川村 淳; 大井 貴夫; 新里 忠史; 安江 健一; 梅田 浩司; 牧野 仁史; 石丸 恒存

no journal, , 




梅木 博之; 大澤 英昭; 内藤 守正; 中野 勝志; 牧野 仁史; 宮本 陽一; 高瀬 博康*; McKinley, I. G.*; 梅田 浩司; 浅森 浩一; et al.

no journal, , 



放射性廃棄物地層処分にかかわる天然現象影響評価研究; 地質環境の長期安定性研究から影響評価に至るまでの一連の研究開発

川村 淳; 大井 貴夫; 梅田 浩司; 新里 忠史; 江橋 健; 北村 暁; 河内 進; 牧野 仁史; 石丸 恒存; 柳川 玄永*; et al.

no journal, , 



放射性廃棄物地層処分にかかわる天然現象影響評価研究; 地質環境条件変化の検討

川村 淳; 大井 貴夫; 梅田 浩司; 新里 忠史; 牧野 仁史; 河内 進; 石丸 恒存; 柳川 玄永*; 大久保 博生*

no journal, , 




川村 淳; 新里 忠史; 安江 健一; 常盤 哲也; 大井 貴夫; 河内 進; 石丸 恒存; 梅田 浩司; 牧野 仁史

no journal, , 



Study on potential changes in geological and disposal environment caused by "natural phenomena" on a HLW disposal system

川村 淳; 梅田 浩司; 大井 貴夫; 石丸 恒存; 新里 忠史; 安江 健一; 牧野 仁史

no journal, , 

JAEA have developed a procedure to assess the potential impact of "natural phenomena" (earthquakes and fault movement; volcanism; uplift, subsidence and denudation; climatic and sea-level changes) on a High Level Radioactive Waste (HLW) Disposal System. This procedure is for describing such perturbation scenarios based on further studies of the characteristics of these natural perturbation phenomena in Japan. This procedure has two advantages. First one is assuring maintenance of traceability during the scenario construction processes, facilitating the production and structuring of suitable records. The second is providing effective elicitation and organization of information from a wide range of investigations of earth sciences within a performance assessment context. In this framework, scenario development work proceeds in a stepwise manner, to ensure clear identification of the impact of processes associated with these phenomena on a HLW disposal system. Output is organized to create credible scenarios with required transparency, consistency, traceability and adequate conservatism.

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