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Revealing defect-induced spin disorder in nanocrystalline Ni

Bersweiler, M.*; Sinaga, E. P.*; Peral, I.*; 足立 望*; Bender, P.*; Steinke, N.-J.*; Gilbert, E. P.*; 戸高 義一*; Michels, A.*; 大場 洋次郎

Physical Review Materials (Internet), 5(4), p.044409_1 - 044409_7, 2021/04

 被引用回数:1 パーセンタイル:69.4(Materials Science, Multidisciplinary)

Using small-angle neutron scattering (SANS), we found that the high-density of crystal defects induced via high-pressure torsion (HPT) straining cause a significant spin-misalignment scattering in pure Ni. The analysis of the correlation length of the spin misalignments provided that the spin misalignments surround the defect with the size of 11 nm in HPT-strained nickel.


Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

 被引用回数:7 パーセンタイル:80.58(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.


$$beta^-$$ decay of $$T_z$$ = +$$frac{11}{2}$$ isotopes $$^{37}$$Al and $$^{39}$$Si; Understanding Gamow-Teller strength distribution in neutron-rich nuclei

Abromeit, B.*; Tripathi, V.*; Crawford, H. L.*; Liddick, S. N.*; 吉田 聡太*; 宇都野 穣; Bender, P. C.*; Crider, B. P.*; Dungan, R.*; Fallon, P.*; et al.

Physical Review C, 100(1), p.014323_1 - 014323_14, 2019/07


 被引用回数:1 パーセンタイル:22.36(Physics, Nuclear)

中性子過剰核$$^{37}$$Al, $$^{39}$$Siとその娘核からのベータ崩壊をミシガン州立大学の国立超伝導サイクロトロン研究所において調べた。ベータ崩壊で得られた準位構造を大規模殻模型計算と比較し、実験と理論の良い一致が得られることがわかった。さらに、脱励起ガンマ線の強度から、それぞれの準位にベータ遷移する強度を表す$$log ft$$値を引き出した。これら奇核のベータ崩壊で得られた低励起状態への$$log ft$$値は偶偶核からのものよりも強くフラグメントしていることがわかった。これは、大規模殻模型計算で予言されたガモフテラー遷移強度の分布に対する一般的傾向に合致した結果である。


$$beta$$ decay of $$^{38,40}$$Si ($$T_z$$ = +5, +6) to low-lying core excited states in odd-odd $$^{38,40}$$P isotopes

Tripathi, V.*; Lubna, R. S.*; Abromeit, B.*; Crawford, H. L.*; Liddick, S. N.*; 宇都野 穣; Bender, P. C.*; Crider, B. P.*; Dungan, R.*; Fallon, P.*; et al.

Physical Review C, 95(2), p.024308_1 - 024308_7, 2017/02


 被引用回数:6 パーセンタイル:57.56(Physics, Nuclear)

ミシガン州立大の超伝導サイクロトロン施設にて中性子過剰核$$^{38,40}$$Siから$$^{38,40}$$Pへのベータ崩壊を測定した。親核の基底状態$$0^+$$からガモフテラー遷移で強く遷移する$$^{38,40}$$Pの$$1^+$$状態を下から3本観測することができた。これらの$$1^+$$状態はコア励起を伴う異常パリティ状態であるにも関わらず、励起エネルギーが1-2MeV領域と低く出現することがわかった。これらの$$1^+$$状態の励起エネルギーおよび$$log ft$$値は殻模型計算によってよく再現できた。$$1^+_1$$状態よりも$$1^+_{2,3}$$状態でガモフテラー遷移強度が大きくなるという実験結果を、これらの原子核の殻構造の観点から理解できることを示した。


Are there signatures of harmonic oscillator shells far from stability?; First spectroscopy of $$^{110}$$Zr

Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Bally, B.*; Bender, M.*; Calvet, D.*; Ch$^a$teau, F.*; et al.

Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01

 被引用回数:27 パーセンタイル:88.56(Physics, Multidisciplinary)

The first measurement of $$gamma$$ rays emitted by the very neutron rich nuclei $$^{112}$$Mo (Z=42) and $$^{110}$$Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state $$^{112}$$Mo and $$^{110}$$Zr, respectively 235(7) keV and 185(11) keV, and their E(4$$^+$$)/E(2$$^+$$) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.


Collectivity in the light radon nuclei measured directly via Coulomb excitation

Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.

Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06

 被引用回数:8 パーセンタイル:57.47(Physics, Nuclear)

Radioactive ion beams of $$^{202,204}$$Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2$$^+$$ to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.


Multi-intruder structures in $$^{34}$$P

Bender, P. C.*; Tabor, S. L.*; Tripathi, V.*; Hoffman, C. R.*; Hamilton, L.*; Volya, A.*; Clark, R. M.*; Fallon, P.*; Macchiavelli, A. O.*; Paschalis, S.*; et al.

Physical Review C, 85(4), p.044305_1 - 044305_10, 2012/04

 被引用回数:12 パーセンタイル:60.36(Physics, Nuclear)

24MeVの$$^{18}$$Oビームと$$^{18}$$Oターゲットの反応で生じるプロトンと同時計数をとった$$gamma$$崩壊の解析によって$$^{34}$$Pの励起準位は大幅に拡張された。軽い荷電粒子はMicroballによって検出され、同時に放出される多重$$gamma$$線はGammasphereで検出された。多くの新しい$$gamma$$線遷移が同定され、励起準位が構築された。加えて、$$gamma$$線角度分布からスピンが特定され、パリティはドップラー幅拡がりの解析によって決定された寿命から推定された。観測されたほとんどの準位は0$$f$$$$_{7/2}$$か1$$p$$$$_{3/2}$$軌道に粒子を持つWBP-aとSDPF-NR相互作用を使ったシェルモデル計算によって理解された。2つの計算は約200keVの範囲でよく一致した。しかし、高エネルギー準位の2つはstretched $$pi$$$$f$$$$_{7/2}$$ $$otimes$$ $$nu$$$$f$$$$_{7/2}$$準位であるかもしれないが、計算はそれらのエネルギーを2から3MeVオーバーしている。さらに新しく観測された長寿命7919-keVは今のところ説明ができない。


Intruder configurations in the A=33 isobars; $$^{33}$$Mg and $$^{33}$$Al

Tripathi, V.*; Tabor, S. L.*; Mantica, P. F.*; 宇都野 穣; Bender, P.*; Cook, J.*; Hoffman, C. R.*; Lee, S.*; 大塚 孝治*; Pereira, J.*; et al.

Physical Review Letters, 101(14), p.142504_1 - 142504_4, 2008/10

 被引用回数:49 パーセンタイル:86.64(Physics, Multidisciplinary)



Excited intruder states in $$^{32}$$Mg

Tripathi, V.*; Tabor, S. L.*; Bender, P.*; Hoffman, C. R.*; Lee, S.*; Pepper, K.*; Perry, M.*; Mantica, P.*; Cook, J. M.*; Pereira, J.*; et al.

Physical Review C, 77(3), p.034310_1 - 034310_8, 2008/03

 被引用回数:28 パーセンタイル:82.41(Physics, Nuclear)



Competition between normal and intruder states inside the "island of inversion"

Tripathi, V.*; Tabor, S. L.*; Mantica, P. F.*; 宇都野 穣; Bender, P.*; Cook, J. M.*; Hoffman, C. R.*; Lee, S.*; 大塚 孝治*; Pereira, J.*; et al.

Physical Review C, 76(2), p.021301_1 - 021301_5, 2007/08

 被引用回数:25 パーセンタイル:83.05(Physics, Nuclear)



Domain wall based spin-Hall nano-oscillators

佐藤 奈々; Schultheiss, K.*; K$"o$rber, L.*; Puwenberg, N.*; M$"u$hl, T.*; Awad, A. A.*; Arekapudi, S. S. P. K.*; Hellwig, O.*; Fassbender, J.*; Schultheiss, H.*

no journal, , 

In the last decade, two revolutionary concepts in nano magnetism emerged from research for advanced information processing and storage technologies. The first suggests the use of magnetic domain walls (DWs) in ferromagnetic nanowires to permanently store information in DW racetrack memories. The second proposes a hardware realisation of neuromorphic computing in nanomagnets using nonlinear magnetic oscillations in the GHz range. Both ideas originate from the transfer of angular momentum from conduction electrons to localised spins in ferromagnets, either to push data encoded in DWs along nanowires or to sustain magnetic oscillations in artificial neurones. Even though both concepts share a common ground, they live on very different time scales which rendered them incompatible so far. Here, we bridge both ideas by demonstrating the excitation of magnetic auto-oscillations inside nano-scale DWs using pure spin currents.


Revealing defect-induced spin disorder in nanocrystalline Ni

Bersweiler, M.*; Sinaga, E. P.*; Peral, I.*; 足立 望*; Bender, P.*; Steinke, N.-J.*; Gilbert, E. P.*; 戸高 義一*; 大場 洋次郎; Michels, A.*

no journal, , 

Magnetic properties of nanocrystalline nickel prepared via high-pressure torsion straining was investigated using magnetometry and magnetic small-angle neutron scattering to study the influence of the microstructure on magnetism. The magnetometry shows a significant increase of the coercivity compared to nondeformed polycrystalline nickel. The neutron data detect a nanoscale spin misalignment caused by the high density of crystal defects created by severe plastic deformation during the sample preparation. These results indicate that magnetic anisotropy is enhanced around the crystal defects.

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