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Journal Articles

Tunnel magnetoresistance exceeding 100% in magnetic tunnel junctions using Mn-based tetragonal alloy electrodes with perpendicular magnetic anisotropy

Suzuki, Kazuya; Mizukami, Shigemi*

AIP Advances (Internet), 13(3), p.035225_1 - 035225_6, 2023/03

 Times Cited Count:0

We studied MgO barrier magnetic tunnel junctions (MTJs) comprising perpendicularly magnetized MnGa and FeCoB electrodes. In those perpendicular ($$p$$-) MTJs, we utilized thin metastable bcc CoMn alloys for an interlayer between MnGa and MgO to enhance the tunnel magnetoresistance (TMR). Moreover, we investigated the effect of a thin Mg interlayer between MnGa and CoMn. Owing to the interlayer engineering, we achieved a TMR ratio over 100%, the highest value observed for $$p$$-MTJs with a tetragonal MnGa electrode. Our study contributes to the further development of spintronic devices using $$p$$-MTJs with various Mn-based tetragonal alloy electrodes.

Journal Articles

EXAFS investigation of strontium adsorption onto weathered biotite

Honda, Mitsunori; Kaneta, Yui; Yaita, Tsuyoshi

AIP Advances (Internet), 13(1), p.015314_1 - 015314_6, 2023/01

 Times Cited Count:0 Percentile:0.01(Nanoscience & Nanotechnology)

The efficiency of the sorption of Sr$$^{2+}$$ on weathered biotite, a type of clay minerals was investigated. Removal of Sr$$^{2+}$$ and Cs$$^{+}$$ is important in the treatment of contaminated water from the 1F accident, which is one of the radionuclide waste treatment problems. We focused on developing an adsorption method for Sr ions using weathered biotite, which are abundant in Fukushima. Applying a molten salt treatment, the amount of sorbed Sr$$^{2+}$$ simply increased as the added mass ratio of strontium chloride (SrCl$$_{2}$$) increased from 1:1, 1:5, and 1:10 for the one-fold, five-fold, and ten-fold additions of SrCl$$_{2}$$, respectively. Then, the crystal structure of weathered biotite as an adsorbent was evaluated by X-ray diffraction (XRD) analysis. Thus, it was observed that the WB retained its original crystal structure even after the sorption of Sr$$^{2+}$$. Extended X-ray absorption fine structure (EXAFS) analysis was performed to investigate the local sorption structure of Sr$$^{2+}$$ in the WB. The results revealed that Sr$$^{2+}$$ was preferentially sorbed into the SiO$$_{4}$$ and Al$$_{2}$$O$$_{3}$$ layers when Sr$$^{2+}$$ was in the low mass ratio, while, it was mainly sorbed into the SiO$$_{4}$$ layer when the ratio was high.

Journal Articles

Features of accelerator-based neutron source for boron neutron capture therapy calculated by Particle and Heavy Ion Transport code System (PHITS)

Matsuya, Yusuke; Kusumoto, Tamon*; Yachi, Yoshie*; Hirata, Yuho; Miwa, Misako*; Ishikawa, Masayori*; Date, Hiroyuki*; Iwamoto, Yosuke; Matsuyama, Shigeo*; Fukunaga, Hisanori*

AIP Advances (Internet), 12(2), p.025013_1 - 025013_9, 2022/02

 Times Cited Count:2 Percentile:66.83(Nanoscience & Nanotechnology)

Boron Neutron Capture Therapy (BNCT) is a radiation therapy, which can selectively eradicate solid tumors by $$alpha$$-particles and Li ions generated through the nuclear reaction between thermal neutron and $$^{10}$$B in tumor cells. With the development of accelerator-based neutron sources that can be installed in medical institutions, accelerator-based boron neutron capture therapy is expected to become available at several medical institutes around the world in the near future. Lithium is one of the targets that can produce thermal neutrons from the $$^{7}$$Li(p,n)$$^{7}$$Be near-threshold reaction. Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo code, which can simulate a variety of diverse particle types and nuclear reactions. The latest PHITS code enables simulating the generation of neutrons from the $$^{7}$$Li(p,n)$$^{7}$$Be reactions by using Japanese Evaluated Nuclear Data Library (JENDL-4.0/HE). In this study, we evaluated the neutron fluence using the PHITS code by comparing it to reference data. The subsequent neutron transport simulations were also performed to evaluate the boron trifluoride (BF$$_{3}$$) detector responses and the recoiled proton fluence detected by a CR-39 plastic detector. As a result, these comparative studies confirmed that the PHITS code can accurately simulate neutrons generated from an accelerator using a Li target. The PHITS code has a significant potential for contributing to more precise evaluating accelerator-based neutron fields and understandings of therapeutic effects of BNCT.

Journal Articles

Bayesian sparse modeling of extended X-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film

Kumazoe, Hiroyuki*; Igarashi, Yasuhiko*; Iesari, F.*; Shimizu, Ryota*; Komatsu, Yuya*; Hitosugi, Taro*; Matsumura, Daiju; Saito, Hiroyuki*; Iwamitsu, Kazunori*; Okajima, Toshihiko*; et al.

AIP Advances (Internet), 11(12), p.125013_1 - 125013_5, 2021/12

 Times Cited Count:1 Percentile:14.03(Nanoscience & Nanotechnology)

Journal Articles

Correlation of anomalous Hall effect with structural parameters and magnetic ordering in Mn$$_{3+x}$$Sn$$_{1-x}$$ thin films

Yoon, J.-Y.*; Takeuchi, Yutaro*; DuttaGupta, S.*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

AIP Advances (Internet), 11(6), p.065318_1 - 065318_6, 2021/06

 Times Cited Count:10 Percentile:79.5(Nanoscience & Nanotechnology)

Journal Articles

Inclination of self-interstitial dumbbells in molybdenum and tungsten; A First-principles study

Suzudo, Tomoaki; Tsuru, Tomohito

AIP Advances (Internet), 11(6), p.065012_1 - 065012_7, 2021/06

 Times Cited Count:2 Percentile:28.94(Nanoscience & Nanotechnology)

In the current study, we analyzed the self-interstitial atoms (SIAs) in BCC molybdenum (Mo) and tungsten (W) in comparison with other BCC transition metals utilizing first-principles method; particularly, we focused on uncommon dumbbells, whose direction are inclined from $$<$$111$$>$$ toward $$<$$110$$>$$ on the {110} plane. Such a direction is not stable neither in the group 5 BCC metals (i.e., vanadium, niobium, and tantalum) nor in $$alpha$$-iron. Our first-principles relaxation simulations indicated that inclined dumbbells were more energetically-favored than common $$<$$111$$>$$ dumbbells in Mo, while this is not necessarily the case for W. However, under a certain degree of lattice strain, such as shear or expansive strain, could make inclined dumbbells more favored also in W, suggesting that the lattice strain can substantially influence the migration barrier of SIAs in these metals because inclined dumbbells generally have a larger migration barrier than $$<$$111$$>$$ dumbbells.

Journal Articles

Geometries and electronic states of iron trimer (Fe$$_{3}$$) by CCSD and CCSD(T) calculations

Nakazawa, Tetsuya

AIP Advances (Internet), 11(4), p.045032_1 - 045032_8, 2021/04

 Times Cited Count:0 Percentile:0(Nanoscience & Nanotechnology)

Geometries and energy separations of various low-lying electronic states of iron trimer (Fe$$_{3}$$) are investigated by CCSD and CCSD(T) calculations. The ground state is found to be a $$^{13}$$A' state with C$$_{s}$$ symmetry, whereas a nearly isoenergetic state, $$^{13}$$A$$_{1}$$ (C$$_{2v}$$), is degenerate to the ground state. The ground and five low-lying states with a spin multiplicity of 13 are found below 0.20 eV at the CCSD(T) level. On the other hand, the low-lying states with spin multiplicities of 9, 11, and 15 appear only above 0.20 eV. From detailed natural bond orbital (NBO) analyses, Fe$$_{3}$$ has Fe-Fe bonds comprised of $$sigma$$-bond orbitals only in $$beta$$-spin part with higher s-character in low-lying states with a spin multiplicity of 13. The polarization coefficients indicate that the $$sigma$$$$_{Fe-Fe}$$ bonds are nearly complete covalent bonds with little polarization.

Journal Articles

Brittle-fracture simulations of curved cleavage cracks in $$alpha$$-iron; A Molecular dynamics study

Suzudo, Tomoaki; Ebihara, Kenichi; Tsuru, Tomohito

AIP Advances (Internet), 10(11), p.115209_1 - 115209_8, 2020/11

 Times Cited Count:6 Percentile:41.49(Nanoscience & Nanotechnology)

The mechanism of their brittle fracture of BCC metals is not fully understood. In this study, we conduct a series of three-dimensional molecular dynamics simulations of cleavage fracture of $$alpha$$-iron. In particular, we focus on mode-I loading starting from curved crack fronts. In the simulations, brittle fractures are observed at cleavages on the {100} plane, while the initial cracks become blunted on other planes as a result of dislocation emissions. Our modeling results agreed with a common experimental observation, that is, {100} is the preferential cleavage plane in bcc transition metals.

Journal Articles

Preparation, thermoelectric properties, and crystal structure of boron-doped Mg$$_{2}$$Si single crystals

Hayashi, Kei*; Saito, Wataru*; Sugimoto, Kazuya*; Oyama, Kenji*; Hayashi, Koichi*; Happo, Naohisa*; Harada, Masahide; Oikawa, Kenichi; Inamura, Yasuhiro; Miyazaki, Yuzuru*

AIP Advances (Internet), 10(3), p.035115_1 - 035115_7, 2020/03

 Times Cited Count:15 Percentile:76.81(Nanoscience & Nanotechnology)

Journal Articles

Magnetic field dependence of the nonlocal spin Seebeck effect in Pt/YIG/Pt systems at low temperatures

Oyanagi, Koichi*; Kikkawa, Takashi*; Saito, Eiji

AIP Advances (Internet), 10(1), p.015031_1 - 015031_5, 2020/01

 Times Cited Count:13 Percentile:72.26(Nanoscience & Nanotechnology)

Journal Articles

Direct observation of electronic structure change by resistance random access memory effect in amorphous alumina

Kubota, Masato; Nigo, Seisuke*; Kato, Seiichi*; Amemiya, Kenta*

AIP Advances (Internet), 9(9), p.095050_1 - 095050_4, 2019/09

 Times Cited Count:0 Percentile:0(Nanoscience & Nanotechnology)

We measured the X-ray absorption spectra of amorphous alumina with vacancy-type oxygen defects which exhibits the resistance random access memory effect. For the first time, we detected changes in the electronic structure owing to the memory effect. A major difference in spectrum was observed near the O K-absorption edge.

Journal Articles

Inverted-parabolic and weak strain dependencies on the critical current in practical $$<$$110$$>$$ and $$<$$100$$>$$ oriented REBCO tapes

Osamura, Kozo*; Machiya, Shutaro*; Kajiwara, Kentaro*; Kawasaki, Takuro; Harjo, S.; Zhang, Y.*; Fujita, Shinji*; Iijima, Yasuhiro*; Hampshire, D. P.*

AIP Advances (Internet), 9(7), p.075216_1 - 075216_11, 2019/07

 Times Cited Count:7 Percentile:43.45(Nanoscience & Nanotechnology)

Journal Articles

Longitudinal strain of epitaxial graphene monolayers on SiC substrates evaluated by $$z$$-polarization Raman microscopy

Saito, Yuika*; Tokiwa, Kenshiro*; Kondo, Takahiro*; Bao, J.*; Terasawa, Tomoo; Norimatsu, Wataru*; Kusunoki, Michiko*

AIP Advances (Internet), 9(6), p.065314_1 - 065314_6, 2019/06

 Times Cited Count:2 Percentile:12.38(Nanoscience & Nanotechnology)

Journal Articles

Superconductivity in a multiorbital model for the $$Gamma_3$$ crystalline electric field state

Kubo, Katsunori

AIP Advances (Internet), 8(10), p.101313_1 - 101313_6, 2018/10

 Times Cited Count:3 Percentile:16.95(Nanoscience & Nanotechnology)

Journal Articles

Al-impurity-induced magnetic excitations in heavily over-doped La$$_{1.7}$$Sr$$_{0.3}$$Cu$$_{0.95}$$Al$$_{0.05}$$O$$_{4}$$

Ikeuchi, Kazuhiko*; Nakajima, Kenji; Kawamura, Seiko; Kajimoto, Ryoichi; Wakimoto, Shuichi; Suzuki, Kensuke*; Fujita, Masaki*

AIP Advances (Internet), 8(10), p.101318_1 - 101318_5, 2018/10

 Times Cited Count:0 Percentile:0(Nanoscience & Nanotechnology)

By means of inelastic neutron scattering, we measured magnetic excitations in a sizable single crystal of La$$_{1.7}$$Sr$$_{0.3}$$Cu$$_{0.95}$$Al$$_{0.05}$$O$$_{4}$$, which is an Al-substituted system of the heavily hole-doped cuprate system La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with an effective concentration of holes of $$X_{rm eff}$$ = 0.25.

Journal Articles

Schottky specific heat of the lightly Mn-substituted electron-doped SrTiO$$_3$$

Okuda, Tetsuji*; Kajimoto, Ryoichi; Noda, Masaaki*; Kuwahara, Hideki*

AIP Advances (Internet), 8(10), p.101339_1 - 101339_5, 2018/10

 Times Cited Count:0 Percentile:0(Nanoscience & Nanotechnology)

Journal Articles

Effects of Fe doping on anomalous specific heat and XAFS oscillation in antiferromagnetic metal Mn$$_3$$Si

Hiraka, Haruhiro*; Oyama, Kenji*; Kosaka, Masashi*; Matsumura, Daiju

AIP Advances (Internet), 8(10), p.101424_1 - 101424_5, 2018/10

 Times Cited Count:1 Percentile:5.11(Nanoscience & Nanotechnology)

Journal Articles

Origin of 6-fold coordinated aluminum at (010)-type pyrophyllite edges

Okumura, Masahiko; Sassi, M.*; Rosso, K. M.*; Machida, Masahiko

AIP Advances (Internet), 7(5), p.055211_1 - 055211_9, 2017/05

 Times Cited Count:6 Percentile:32.15(Nanoscience & Nanotechnology)

no abstracts in English

Journal Articles

New p- and n-type ferromagnetic semiconductors; Cr-doped BaZn$$_{2}$$As$$_{2}$$

Gu, B.; Maekawa, Sadamichi

AIP Advances (Internet), 7(5), p.055805_1 - 055805_6, 2017/05

 Times Cited Count:4 Percentile:22.07(Nanoscience & Nanotechnology)

Journal Articles

Temperature dependence of the spin Seebeck effect in [Fe$$_{3}$$O$$_{4}$$/Pt]n multilayers

Ramos, R.*; Kikkawa, Takashi*; Anad$'o$n, A.*; Lucas, I.*; Uchida, Kenichi*; Algarabel, P. A.*; Morell$'o$n, L.*; Aguirre, M. H.*; Saito, Eiji; Ibarra, M. R.*

AIP Advances (Internet), 7(5), p.055915_1 - 055915_7, 2017/05

 Times Cited Count:17 Percentile:65.69(Nanoscience & Nanotechnology)

27 (Records 1-20 displayed on this page)