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

久保田 正人; 児子 精祐*; 加藤 誠一*; 雨宮 健太*

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

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)



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

長村 光造*; 町屋 修太郎*; 梶原 堅太郎*; 川崎 卓郎; Harjo, S.; Zhang, Y.*; 藤田 真司*; 飯島 康裕*; Hampshire, D. P.*

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

 被引用回数:1 パーセンタイル:71.33(Nanoscience & Nanotechnology)

In the commercial coated conductor tapes, the twinned structure of REBCO (REBa$$_{2}$$Cu$$_{3}$$O$$_{7-d}$$, RE = Y and Gd) is characterized as either $$<$$100$$>$$ or $$<$$110$$>$$ orientation based on the tape length direction. In this study, we investigate the effects of the two different twinned structures on the critical current $$I_{rm c}$$ of the REBCO tapes by combining; transport critical current and synchrotron radiation diffraction measurements. For the tapes with $$<$$100$$>$$ oriented twins, we observed the inverted parabolic strain behavior on the uniaxial strain dependence of $$I_{rm c}$$. In contrast, the ones with $$<$$110$$>$$ oriented twins showed a weak strain behavior without any maximum appeared in the strain dependence. Such a different uniaxial strain dependence was analyzed by using the one-dimensional twin model with different fractional lengths of A-domains and B-domains of REBCO twins. This model explains the essential features of the different uniaxial strain dependence we observed.


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

齊藤 結花*; 常磐 拳志郎*; 近藤 崇博*; Bao, J.*; 寺澤 知潮; 乗松 航*; 楠 美智子*

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

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)

Longitudinal strains in epitaxial monolayer graphene (EMG) grown on SiC substrates were evaluated by $$z$$-polarization Raman microscopy. Due to the covalent bonds formed at the interface between graphene and the substrate, strong compressive strains were loaded on the EMG, which were sensitively detected by Raman spectroscopy. Our polarization Raman microscope was specially designed for evaluating the longitudinal ($$z$$-polarization) strain, as well as the lateral ($$xy$$-polarization). $$Z$$-polarization Raman microscopy revealed the relationship between the fluctuation of the local strains and the sample morphology in the SiC-graphene through submicron spatial resolution mapping. The amount of strain estimated through Raman shift and its spatial inhomogeneity have critical influence on the mobility of electrons, which are essential for future device applications of EMG.


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

久保 勝規

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

 被引用回数:3 パーセンタイル:73.51(Nanoscience & Nanotechnology)

A cubic system with the $$Gamma_3$$ cubic crystalline electric field (CEF) state is an ideal system to investigate multipole physics, since it does not have dipole but has higher-order multipoles such as quadrupole and octupole. In addition, superconductivity has been observed in PrT$$_2$$X$$_{20}$$ (T = Ir, Rh, X = Zn; T = Ti, V, X = Al) systems with the $$Gamma_3$$ CEF ground state. To approach these phenomena theoretically, we consider a model composed of f electrons with the total angular momentum $$j=5/2$$. From this model, we have derived multipole interactions for the $$Gamma_3$$ systems. In the present study, we investigate superconductivity in the same model. We apply random phase approximation for superconductivity in a multiorbital system to the present model. Then, we have obtained a d-wave spin-singlet state. We will discuss the relevance of the present theory to the PrT$$_2$$X$$_{20}$$ superconductors.


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

池内 和彦*; 中島 健次; 河村 聖子; 梶本 亮一; 脇本 秀一; 鈴木 謙介*; 藤田 全基*

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

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)



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

奥田 哲治*; 梶本 亮一; 野田 正亮*; 桑原 英樹*

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

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)

Large changes in the low-temperature specific heat (low-$$TC$$) by applying magnetic fields up to 9 Tesla were found in the lightly Mn-substituted electron-doped perovskites Sr$$_{1-x}$$La$$_{x}$$TiO$$_{3}$$. The changes in the low-$$TC$$ are qualitatively well explained by the Schottky specific heat ($$C_mathrm{Sch}$$) of localized spins of the Mn 3d electrons in weak internal magnetic fields via itinerant electrons. According to the analysis by using the conventional model, the doped Mn ions are apparently not Mn$$^{4+}$$ ($$S$$ = 3/2) ions, but are Jahn-Teller active Mn$$^{3+}$$ ($$S$$ = 2) ions or mixtures of Mn$$^{3+}$$ and Mn$$^{2+}$$ ions. However, the actual numbers of localized spins estimated from $$C_mathrm{Sch}$$ are about 30% smaller than the expected values. Part of the localized spins of the Mn 3d electrons may disappear due to Kondo coupling with the itinerant electrons, leading to the observed enhancement of the electronic specific heat coefficients.


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

平賀 晴弘*; 大山 研司*; 小坂 昌史*; 松村 大樹

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

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)

The specific heat of Mn$$_{3-x}$$Fe$$_x$$Si was measured over a wide temperature range. Aside from the lattice and electronic specific heat components, another component had a significant contribution to the specific heat at low temperatures in the case of $$x$$ = 0.2; however, its contribution decreased when $$x$$ = 1.0. It is observed that the net component was retained at temperatures significantly higher than $$T_N$$ for both $$x$$. The XAFS spectra of the Mn $$K$$-edge for $$x$$ = 0 not only indicated a smooth structure near the edge, but also an unusually small amplitude in the extended high energy region; however, these features disappeared with Fe doping. The specific heat and XAFS data were discussed interms of the charge degree of freedom or electronic inhomogeneity.


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

奥村 雅彦; Sassi, M.*; Rosso, K. M.*; 町田 昌彦

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

 被引用回数:5 パーセンタイル:55.44(Nanoscience & Nanotechnology)



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

Gu, B.; 前川 禎通

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

 被引用回数:2 パーセンタイル:80.54(Nanoscience & Nanotechnology)

We find new ferromagnetic semiconductors, Cr-doped BaZn$$_{2}$$As$$_{2}$$, by employing a combined method of the density functional theory and the quantum Monte Carlo simulation. Due to a narrow band gap of 0.2 eV in host BaZn$$_{2}$$As$$_{2}$$ and the different hybridization of 3d orbitals of Cr impurity, the impurity bound states have been induced both below the top of valence band and above the bottom of conduction band. The long-range ferromagnetic coupling between Cr impurities is obtained with both p- and n-type carriers.


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

Ramos, R.*; 吉川 貴史*; Anad$'o$n, A.*; Lucas, I.*; 内田 健一*; Algarabel, P. A.*; Morell$'o$n, L.*; Aguirre, M. H.*; 齊藤 英治; Ibarra, M. R.*

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

 被引用回数:13 パーセンタイル:24.22(Nanoscience & Nanotechnology)

We report temperature dependent measurements of the spin Seebeck effect (SSE) in multilayers formed by repeated growth of a Fe$$_3$$O$$_4$$/Pt bilayer junction. The magnitude of the observed enhancement of the SSE, relative to the SSE in the single bilayer, shows a monotonic increase with decreasing the temperature. This result can be understood by an increase of the characteristic length for spin current transport in the system, in qualitative agreement with the recently observed increase in the magnon diffusion length in Fe$$_3$$O$$_4$$ at lower temperatures. Our result suggests that the thermoelectric performance of the SSE in multilayer structures can be further improved by careful choice of materials with suitable spin transport properties.


Magnetocaloric effect of Sr-substituted BaFeO$$_{3}$$ in the liquid nitrogen and natural gas temperature regions

吉井 賢資; 林 直顕*; 水牧 仁一朗*; 高野 幹夫*

AIP Advances (Internet), 7(4), p.045117_1 - 045117_6, 2017/04

 被引用回数:2 パーセンタイル:80.54(Nanoscience & Nanotechnology)

本研究では、川崎市の明治大学生田キャンパスにおいて、土壌を深さ30cmまでコアサンプラーを用いて採取し、逐次抽出法を適用することで、放射性セシウムの深度別存在形態分析を行った。土壌試料は、生田キャンパス内の人の手が加えられていない6地点で、植生を考慮し採取した。表層土壌を一地点につき、深度別形態分析用の土壌を採取するポイントを中心に、30cm四方の4点(深さ5cm)でスコップを用いて採取した。また、生田キャンパスの北東で、コアサンプラーを用いて、深さ30cm分の土壌を採取した。採取したコア土壌は、5cmごとに分割し、ねじ口U-8式容器に充填した。放射性セシウム濃度は深度別に、2.5Bq kg$$^{-1}$$ (0-5cm)、22.3Bq kg$$^{-1}$$ (5-10cm)、3.4Bq kg$$^{-1}$$ (10-15cm)、0.3Bq kg$$^{-1}$$ (15-20cm)、0.8Bq kg$$^{-1}$$ (20-25cm)、1.0Bq kg$$^{-1}$$ (25-30cm)であった。川崎市で採取した土壌中の放射性セシウムは、表層から土壌の深さ方向に浸透していることが示唆される。


Linear magnetoresistance in a topological insulator Ru$$_2$$Sn$$_3$$

塩見 雄毅*; 齊藤 英治

AIP Advances (Internet), 7(3), p.035011_1 - 035011_6, 2017/03

 被引用回数:3 パーセンタイル:71.21(Nanoscience & Nanotechnology)

We have studied magnetotransport properties of a topological insulator material Ru$$_2$$Sn$$_3$$. Bulk single crystals of Ru$$_2$$Sn$$_3$$ were grown by a Bi flux method. The resistivity is semiconducting at high temperatures above 160 K, while it becomes metallic below 160 K. Nonlinear field dependence of Hall resistivity in the metallic region shows conduction of multiple carriers at low temperatures. In the high-temperature semiconducting region, magnetoresistance exhibits a conventional quadratic magnetic-field dependence. In the low-temperature metallic region, however, high-field magnetoresistance is clearly linear with magnetic fields, signaling a linear dispersion in the low-temperature electronic structure. Small changes in the magnetoresistance magnitude with respect to the magnetic field angle indicate that bulk electron carriers are responsible mainly for the observed linear magnetoresistance.


Real-time observation of rotational twin formation during molecular-beam epitaxial growth of GaAs on Si (111) by X-ray diffraction

鈴木 秀俊*; 仲田 侑加*; 高橋 正光; 池田 和磨*; 大下 祥雄*; 諸原 理*; 外賀 寛崇*; 森安 嘉貴*

AIP Advances (Internet), 6(3), p.035303_1 - 035303_6, 2016/03

 被引用回数:4 パーセンタイル:68.28(Nanoscience & Nanotechnology)

The formation and evolution of rotational twin (TW) domains introduced by a stacking fault during molecular-beam epitaxial growth of GaAs on Si (111) substrates were studied by in situ X-ray diffraction. To modify the volume ratio of TW to total GaAs domains, GaAs was deposited under high and low group V/group III (V/III) flux ratios. For low V/III, there was less nucleation of TW than normal growth (NG) domains, although the NG and TW growth rates were similar. For high V/III, the NG and TW growth rates varied until a few GaAs monolayers were deposited; the mean TW domain size was smaller for all film thicknesses.


A Predictive model for transferability of plastic deformation through grain boundaries

都留 智仁; 渋谷 陽二*; 廣内 智之*

AIP Advances (Internet), 6(1), p.015004_1 - 015004_9, 2016/01

 被引用回数:4 パーセンタイル:68.28(Nanoscience & Nanotechnology)



Construction of a magnetic bottle spectrometer and its application to pulse duration measurement of X-ray laser using a pump-probe method

難波 愼一*; 長谷川 登; 岸本 牧; 錦野 将元; 石野 雅彦; 河内 哲哉

AIP Advances (Internet), 5(11), p.117101_1 - 117101_10, 2015/11

 被引用回数:0 パーセンタイル:100(Nanoscience & Nanotechnology)



Spin-current injection and detection in $$kappa$$-(BEDT-TTF)$$_{2}$$Cu[N(CN)$$_{2}$$]Br

Qiu, Z.*; 賣市 幹大*; Hou, D.*; 内田 健一*; 山本 浩史*; 齊藤 英治

AIP Advances (Internet), 5(5), p.057167_1 - 057167_7, 2015/05

 被引用回数:14 パーセンタイル:34.26(Nanoscience & Nanotechnology)

Spin-current injection into an organic semiconductor $$kappa$$-(BEDT-TTF)$$_{2}$$Cu[N(CN)$$_{2}$$]Br film induced by the spin pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage signal was found to appear in the $$kappa$$-(BEDT-TTF)$$_{2}$$Cu[N(CN)$$_{2}$$]Br film. Magnetic-field-angle dependence measurements indicate that the voltage signal is governed by the inverse spin Hall effect in $$kappa$$-(BEDT-TTF)$$_{2}$$Cu[N(CN)$$_{2}$$]Br. We found that the voltage signal in the $$kappa$$-(BEDT-TTF)$$_{2}$$Cu[N(CN)$$_{2}$$]Br/YIG system is critically suppressed around 80 K, around which magnetic and/or glass transitions occur, implying that the efficiency of the spin-current injection is suppressed by fluctuations which critically enhanced near the transitions.


Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

新関 智彦*; 吉川 貴史*; 内田 健一*; 岡 美嶺人*; 鈴木 和也*; 柳原 英人*; 喜多 英治*; 齊藤 英治

AIP Advances (Internet), 5(5), p.053603_1 - 053603_6, 2015/05

 被引用回数:28 パーセンタイル:16.7(Nanoscience & Nanotechnology)

The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. Externalmagnetic-field ($$H$$) dependence of the LSSE voltage ($$V_{LSSE}$$) in the Pt/CFO(110) sample with $$H |[001]$$ was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with $$H |[1 overline{1} 0]$$ shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of $$V_{LSSE}$$ has a linear relationship with the temperature difference ($$Delta T$$), giving the relatively large $$V_{LSSE}$$/$$Delta T$$ of about 3 $$mu$$V/K for CFO(110) which was kept even at zero external field.

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