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Start Over Author "Yamamoto, A." Journal applied physics letters
2,210 results on '"Yamamoto, A."'

3. Emergence of chirality from electron spins, physical fields, and material-field composites.

Author

Kusunose, Hiroaki, Kishine, Jun-ichiro, and Yamamoto, Hiroshi M.

Subjects
ELECTRON spin, CHIRALITY, MATERIALS science, DEGREES of freedom, HANDEDNESS
Abstract

In this work, chirality in spin-active electronic states is explained clearly to address confusion about chiral effects recently discovered in materials science. We stress that the electronic toroidal monopole G0 can serve as a measure of chirality. By using the symmetry classification in terms of four distinct types of multipole bases, we extend the concept of chirality from materials to physical fields and material-field composites. Additionally, we illustrate specific examples from physics and chemistry that demonstrate the process of acquiring chirality through the combination of seemingly achiral degrees of freedom, which we term the emergence of chirality. Interference between multiple chiralities exhibiting phenomena specific to handedness is also discussed. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Phonon drag thermopower persisting over 200 K in FeSb2 thin film on SrTiO3 single crystal.

Author

Yamamoto, Chihiro, He, Xinyi, Hanzawa, Kota, Katase, Takayoshi, Sasase, Masato, Yamaura, Jun-ichi, Hiramatsu, Hidenori, Hosono, Hideo, and Kamiya, Toshio

Subjects
*THIN films, *THERMOELECTRIC power, *SINGLE crystals, *PHONONS, *THERMOELECTRIC cooling
Abstract

FeSb2 is known as a potential low-temperature thermoelectric material with the record-high power factor (PF) originating from the huge phonon drag thermopower (Sg). However, the Sg contribution to PF has been observed only at very low temperatures (T) < 40 K. In this paper, we found that the Sg persists at much higher T up to 240 K and enhances PF in FeSb2 thin films deposited on SrTiO3 single crystals. The FeSb2 films showed phonon drag Sg peak at T ∼ 60 K, and the Sg peak value was largely enhanced from 56 to 208 μV/K by varying film thicknesses from 10 to 100 nm. Due to thickness-dependent Sg contribution, the maximum PF = 31.3 μW/(cm K2) was obtained for a 37-nm thick film. In addition, the onset temperature, where Sg starts to appear, can be largely increased due presumably to the enhanced electron–phonon interaction by phonon leakage from the SrTiO3 substrate to the thin FeSb2 layer. Heterostructuring with an oxide would be an effective approach to enhance the phonon drag effect to increase PF in higher T regions for future thermoelectric cooling and energy conversion devices. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Luminescence coupling in 28.4%-efficient tandem solar cell utilizing 20.8%-efficient perovskite minimodule stacked on silicon cell

Author

Mishima, Ryota, primary, Yoshida, Wataru, additional, Ishibashi, Hirotaka, additional, Tanaka, Haruki, additional, Kishimoto, Kazuhisa, additional, Hino, Masashi, additional, Kanematsu, Masanori, additional, Okamoto, Shimpei, additional, Fujimoto, Takahisa, additional, Koizumi, Gensuke, additional, Uzu, Hisashi, additional, Adachi, Daisuke, additional, and Yamamoto, Kenji, additional

Published
2023
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7. A circular photogalvanic effect in two-dimensional electron gas on the surface of SrTiO3.

Author

Yamamoto, Mahiro, Nishijima, Taiki, Ohshima, Ryo, Ando, Yuichiro, and Shiraishi, Masashi

Subjects
*PHOTOCONDUCTIVITY, *TWO-dimensional electron gas, *ELECTRON gas, *SPIN-orbit interactions, *CARRIER density, *OPTICAL polarization, *CARRIER gas
Abstract

A spin-splitting state due to a Rashba-type spin–orbit interaction is investigated using two-dimensional electron gas (2DEG) at the surface of SrTiO3. The circular photogalvanic effect is utilized to detect the spin-splitting state. Both the polarization and incident light angle dependence of the measured photocurrent generated in the 2DEG unequivocally show the presence of surface spin splitting in the 2DEG, and variation of the carrier densities of the 2DEG provides further supporting evidence. This finding could pave the way for investigating spin textures and spin physics in two-dimensional carrier gas systems. [ABSTRACT FROM AUTHOR]

Published
2024
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8. A circular photogalvanic effect in two-dimensional electron gas on the surface of SrTiO3.

Author

Yamamoto, Mahiro, Nishijima, Taiki, Ohshima, Ryo, Ando, Yuichiro, and Shiraishi, Masashi

Subjects
PHOTOCONDUCTIVITY, TWO-dimensional electron gas, ELECTRON gas, SPIN-orbit interactions, CARRIER density, OPTICAL polarization, CARRIER gas
Abstract

A spin-splitting state due to a Rashba-type spin–orbit interaction is investigated using two-dimensional electron gas (2DEG) at the surface of SrTiO3. The circular photogalvanic effect is utilized to detect the spin-splitting state. Both the polarization and incident light angle dependence of the measured photocurrent generated in the 2DEG unequivocally show the presence of surface spin splitting in the 2DEG, and variation of the carrier densities of the 2DEG provides further supporting evidence. This finding could pave the way for investigating spin textures and spin physics in two-dimensional carrier gas systems. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Searching for the causes of anomalous Advanced LIGO noise

Author

Berger, B. K., primary, Areeda, J. S., additional, Barker, J. D., additional, Effler, A., additional, Goetz, E., additional, Helmling-Cornell, A. F., additional, Lantz, B., additional, Lundgren, A. P., additional, Macleod, D. M., additional, McIver, J., additional, Mittleman, R., additional, Nguyen, P., additional, Pele, A., additional, Pham, H., additional, Rangnekar, P., additional, Rink, K., additional, Schofield, R. M. S., additional, Smith, J. R., additional, Soni, S., additional, Warner, J., additional, Abbott, R., additional, Adhikari, R. X., additional, Ananyeva, A., additional, Appert, S., additional, Arai, K., additional, Asali, Y., additional, Aston, S. M., additional, Baer, A. M., additional, Ball, M., additional, Ballmer, S. W., additional, Banagiri, S., additional, Barker, D., additional, Barsotti, L., additional, Betzwieser, J., additional, Bhattacharjee, D., additional, Billingsley, G., additional, Biscans, S., additional, Blair, C. D., additional, Blair, R. M., additional, Bode, N., additional, Booker, P., additional, Bork, R., additional, Brooks, A. F., additional, Brown, D. D., additional, Cahillane, C., additional, Chen, X., additional, Ciobanu, A. A., additional, Clara, F., additional, Compton, C. M., additional, Cooper, S. J., additional, Corley, K. R., additional, Countryman, S. T., additional, Covas, P. B., additional, Coyne, D. C., additional, Datrier, L. E. H., additional, Davis, D., additional, Di Fronzo, C., additional, Dooley, K. L., additional, Driggers, J. C., additional, Dwyer, S. E., additional, Etzel, T., additional, Evans, M., additional, Evans, T. M., additional, Feicht, J., additional, Fernandez-Galiana, A., additional, Fritschel, P., additional, Frolov, V. V., additional, Fulda, P., additional, Fyffe, M., additional, Giaime, J. A., additional, Giardina, K. D., additional, Godwin, P., additional, Gras, S., additional, Gray, C., additional, Gray, R., additional, Green, A. C., additional, Gupta, A., additional, Gustafson, E. K., additional, Gustafson, R., additional, Hanks, J., additional, Hanson, J., additional, Hasskew, R. K., additional, Heintze, M. C., additional, Holland, N. A., additional, Kandhasamy, S., additional, Karki, S., additional, Kasprzack, M., additional, Kawabe, K., additional, Kijbunchoo, N., additional, King, P. J., additional, Kissel, J. S., additional, Kumar, Rahul, additional, Landry, M., additional, Lane, B. B., additional, Laxen, M., additional, Lecoeuche, Y. K., additional, Leviton, J., additional, Liu, J., additional, Lormand, M., additional, Macas, R., additional, MacInnis, M., additional, Mansell, G. L., additional, Márka, S., additional, Márka, Z., additional, Martynov, D. V., additional, Mason, K., additional, Matichard, F., additional, Mavalvala, N., additional, McCarthy, R., additional, McClelland, D. E., additional, McCormick, S., additional, McCuller, L., additional, McRae, T., additional, Mendell, G., additional, Merfeld, K., additional, Merilh, E. L., additional, Meylahn, F., additional, Mistry, T., additional, Moreno, G., additional, Mow-Lowry, C. M., additional, Mozzon, S., additional, Mullavey, A., additional, Nelson, T. J. N., additional, Nuttall, L. K., additional, Oberling, J., additional, Oram, Richard J., additional, Osthelder, C., additional, Ottaway, D. J., additional, Overmier, H., additional, Parker, W., additional, Payne, E., additional, Penhorwood, R., additional, Perez, C. J., additional, Pirello, M., additional, Ramirez, K. E., additional, Richardson, J. W., additional, Riles, K., additional, Robertson, N. A., additional, Rollins, J. G., additional, Romel, C. L., additional, Romie, J. H., additional, Ross, M. P., additional, Ryan, K., additional, Sadecki, T., additional, Sanchez, E. J., additional, Sanchez, L. E., additional, Saravanan, T. R., additional, Savage, R. L., additional, Schaetzl, D., additional, Schnabel, R., additional, Schwartz, E., additional, Sellers, D., additional, Shaffer, T., additional, Sigg, D., additional, Slagmolen, B. J. J., additional, Sorazu, B., additional, Spencer, A. P., additional, Sun, L., additional, Szczepańczyk, M. J., additional, Thomas, M., additional, Thomas, P., additional, Thorne, K. A., additional, Toland, K., additional, Torrie, C. I., additional, Traylor, G., additional, Tse, M., additional, Vajente, G., additional, Valdes, G., additional, Vander-Hyde, D. C., additional, Veitch, P. J., additional, Venugopalan, G., additional, Viets, A. D., additional, Vorvick, C., additional, Wade, M., additional, Ward, R. L., additional, Weaver, B., additional, Weiss, R., additional, Whittle, C., additional, Willke, B., additional, Wipf, C. C., additional, Xiao, L., additional, Yamamoto, H., additional, Yu, Hang, additional, Yu, Haocun, additional, Zhang, L., additional, Zucker, M. E., additional, and Zweizig, J., additional

Published
2023
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15. Magnetic field-induced phase transition in ilmenite-type CoVO3.

Author

Yamamoto, Hajime, Wu, Hung-Cheng, Miyake, Atsushi, Tokunaga, Masashi, Suzuki, Akio, Honda, Takashi, and Kimura, Hiroyuki

Subjects
*MAGNETIC transitions, *MAGNETIC structure, *PHASE transitions, *MAGNETIC measurements, *SPONTANEOUS magnetization, *ANTIFERROMAGNETIC materials
Abstract

The ilmenite-type CoVO3 undergoes an antiferromagnetic transition below 140 K, and the tetravalent vanadium ions form V–V dimers below 550 K. This paper presents the magnetic spin structure and the phase transition induced by a magnetic field in CoVO3. Neutron powder diffraction at 50 K reveals that the spins of Co2+ arrange in a zigzag order on the honeycomb lattice with no external magnetic field. This magnetic spin structure does not exhibit spontaneous magnetization, corroborating previous magnetic measurements. Magnetization measurements in a pulsed-magnetic field revealed a transition to a weak-ferromagnetic phase at 37 T (100 K) and above 50 T (4.2 K), with spontaneous magnetization approximating 0.3–0.5 μB/f.u. This phase transition could potentially be attributed to a transition to a canted antiferromagnetic phase, which is brought about by the reduction in structural symmetry due to magnetostriction. [ABSTRACT FROM AUTHOR]

Published
2023
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16. Magnetic field-induced phase transition in ilmenite-type CoVO3.

Author

Yamamoto, Hajime, Wu, Hung-Cheng, Miyake, Atsushi, Tokunaga, Masashi, Suzuki, Akio, Honda, Takashi, and Kimura, Hiroyuki

Subjects
MAGNETIC transitions, MAGNETIC structure, PHASE transitions, MAGNETIC measurements, SPONTANEOUS magnetization, ANTIFERROMAGNETIC materials
Abstract

The ilmenite-type CoVO3 undergoes an antiferromagnetic transition below 140 K, and the tetravalent vanadium ions form V–V dimers below 550 K. This paper presents the magnetic spin structure and the phase transition induced by a magnetic field in CoVO3. Neutron powder diffraction at 50 K reveals that the spins of Co2+ arrange in a zigzag order on the honeycomb lattice with no external magnetic field. This magnetic spin structure does not exhibit spontaneous magnetization, corroborating previous magnetic measurements. Magnetization measurements in a pulsed-magnetic field revealed a transition to a weak-ferromagnetic phase at 37 T (100 K) and above 50 T (4.2 K), with spontaneous magnetization approximating 0.3–0.5 μB/f.u. This phase transition could potentially be attributed to a transition to a canted antiferromagnetic phase, which is brought about by the reduction in structural symmetry due to magnetostriction. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Partial cation disorder in Li2MnO3 obtained by high-pressure synthesis

Author

Abulikemu, Aierxiding, primary, Gao, Shenghan, additional, Matsunaga, Toshiyuki, additional, Takatsu, Hiroshi, additional, Tassel, Cédric, additional, Kageyama, Hiroshi, additional, Saito, Takashi, additional, Watanabe, Toshiki, additional, Uchiyama, Tomoki, additional, Yamamoto, Kentaro, additional, Uchimoto, Yoshiharu, additional, and Takami, Tsuyoshi, additional

Published
2022
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20. Strain-induced massless Dirac fermion state of the molecular conductor α-(BEDT-TTF)2I3

Author

Yoshitaka Kawasugi, Haruto Suzuki, Hiroshi M. Yamamoto, Reizo Kato, and Naoya Tajima

Subjects
Physics and Astronomy (miscellaneous)
Abstract

Uniaxial pressure can dramatically change the properties of low-dimensional systems and induce electronic phase transitions. The first-discovered molecular massless Dirac electron system α-(BEDT-TTF)2I3 has intensively been studied because of its unique features, such as the Fermi energy being very close to the Dirac point, strong electron correlation, and the quantum phase transition from the charge-ordered insulating state. However, the Dirac state is realized only under high pressure of 15 kbar, which limits the measurement of physical properties (e.g., experimental determination of band dispersion and density of states). Here, we demonstrate that the Dirac state of α-(BEDT-TTF)2I3 can be realized by applying uniaxial bending strain without confining it in a pressure cell. Uniaxial strain below 1% completely suppresses the metal–insulator transition observed at ambient pressure. Under strain, a characteristic temperature dependence of magnetoresistance associated with the formation of the n = 0 Landau level is observed, indicating the realization of the massless Dirac state.

Published
2023

21. Robust Si/Ge heterostructure metasurfaces as building blocks for wavelength-selective photodetectors

Author

J. Schlipf, F. Berkmann, Y. Yamamoto, M. Reichenbach, M. Veleski, Y. Kawaguchi, F. Mörz, J. W. Tomm, D. Weißhaupt, and I. A. Fischer

Subjects
Physics and Astronomy (miscellaneous)
Abstract

We present a design for silicon-compatible vertical Germanium pin photodiodes structured into all-dielectric metasurfaces. Proof-of-principle metasurfaces are fabricated on silicon-on-insulator wafers in a top-down process. Simulations and measurements of the spectroscopic properties, specifically the absorption, show high spectral selectivity, and absorption efficiencies as large as those in bulk Germanium layers with about four times the Ge layer thicknesses. Our metasurface structures can be tuned to the target wavelength through tailoring of the lateral geometry. Possible applications include spectroscopy and hyperspectral imaging, with several metasurfaces for different wavelength ranges integrated with readout circuitry into a low-cost electronic–photonic integrated circuit.

Published
2023

22. Strain-induced massless Dirac fermion state of the molecular conductor α-(BEDT-TTF)2I3.

Author

Kawasugi, Yoshitaka, Suzuki, Haruto, Yamamoto, Hiroshi M., Kato, Reizo, and Tajima, Naoya

Subjects
ORGANIC conductors, QUANTUM phase transitions, METAL-insulator transitions, ELECTRON configuration, FERMI energy, LANDAU levels, FERMIONS
Abstract

Uniaxial pressure can dramatically change the properties of low-dimensional systems and induce electronic phase transitions. The first-discovered molecular massless Dirac electron system α-(BEDT-TTF)2I3 has intensively been studied because of its unique features, such as the Fermi energy being very close to the Dirac point, strong electron correlation, and the quantum phase transition from the charge-ordered insulating state. However, the Dirac state is realized only under high pressure of 15 kbar, which limits the measurement of physical properties (e.g., experimental determination of band dispersion and density of states). Here, we demonstrate that the Dirac state of α-(BEDT-TTF)2I3 can be realized by applying uniaxial bending strain without confining it in a pressure cell. Uniaxial strain below 1% completely suppresses the metal–insulator transition observed at ambient pressure. Under strain, a characteristic temperature dependence of magnetoresistance associated with the formation of the n = 0 Landau level is observed, indicating the realization of the massless Dirac state. [ABSTRACT FROM AUTHOR]

Published
2023
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24. Evaluation of degradation behavior in quantum dot light-emitting diode with different hole transport materials via transient electroluminescence

Author

Doe, Takahiro, primary, Kitano, Keisuke, additional, Yamamoto, Satoru, additional, Yamamoto, Masaki, additional, Goto, Kazuki, additional, Sakakibara, Yusuke, additional, Kobashi, Tadashi, additional, Yamada, Hirohisa, additional, Ueda, Masaya, additional, Ryowa, Tatsuya, additional, Izumi, Makoto, additional, and Arakawa, Yasuhiko, additional

Published
2021
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28. Voltage-controlled magnetic anisotropy effect through a LiF/MgO hybrid tunneling barrier

Author

Takayuki Nozaki, Tomohiro Nozaki, Tatsuya Yamamoto, Makoto Konoto, Atsushi Sugihara, Kay Yakushiji, and Shinji Yuasa

Subjects
Physics and Astronomy (miscellaneous)
Abstract

Improving the perpendicular magnetic anisotropy (PMA) and voltage-controlled magnetic anisotropy (VCMA) properties are fundamentally important for the development of voltage-controlled magnetoresistive random access memories (VC-MRAM). Recently, we reported on a large increase in PMA at an Fe/MgO interface brought about by inserting an ultrathin LiF layer at the interface. In this paper, we investigate the PMA, VCMA, and TMR properties in MTJs with an Ir-doped ultrathin ferromagnetic layer and a LiF/MgO hybrid tunneling barrier. We observed a clear increase in the interfacial PMA by a factor of 2.5 when an ultrathin 0.25 nm LiF layer was inserted. A large VCMA coefficient, exceeding −300 fJ/Vm, was also achieved while maintaining the high TMR ratio and high interfacial PMA. These results demonstrate the high potential of interface engineering using ultrathin LiF layers for spintronic devices.

Published
2022

30. Large negative thermal expansion induced by cation dimerization in ilmenite-type vanadate ceramic

Author

Hajime Yamamoto, Sachiko Kamiyama, Takumi Nishikubo, Masaki Azuma, Ikuya Yamada, and Hiroyuki Kimura

Subjects
Physics and Astronomy (miscellaneous)
Abstract

A significant negative thermal expansion (NTE) in an ilmenite-type MgVO3 ceramic is reported in this paper. MgVO3 undergoes V–V dimerization at 500–550 K accompanied by a structural phase transition from the triclinic (low-temperature) to rhombohedral (high-temperature) phase. This transition induces a large anisotropic crystal structure deformation and results in a large NTE in the ceramic sample, which is caused by the microstructural effect. The NTE was observed over a temperature range of 450–630 K, and the total volume shrinkage reached approximately −0.7%. This study demonstrates that controlling the chemical bonding is a promising method for the creation of NTE materials.

Published
2022

31. Partial cation disorder in Li2MnO3 obtained by high-pressure synthesis

Author

Aierxiding Abulikemu, Shenghan Gao, Toshiyuki Matsunaga, Hiroshi Takatsu, Cédric Tassel, Hiroshi Kageyama, Takashi Saito, Toshiki Watanabe, Tomoki Uchiyama, Kentaro Yamamoto, Yoshiharu Uchimoto, and Tsuyoshi Takami

Subjects
Physics and Astronomy (miscellaneous)
Abstract

While atomic disorder has provided a paradigm shift in crystalline materials because of unusual atomic arrangements and functional response, “partial” disorder is scarcely reported until now. We discovered partial cation disorder in Li2MnO3 with fewer stacking faults, which was synthesized under high pressure. Mn and Li atoms in a Mn2/3Li1/3O2 layer disorder while Li atoms in a Li layer order. Magnetization and specific heat measurements indicate a long-range antiferromagnetic (AF) order below 35 K. The irreversibility observed in the magnetization data and the hump observed for the specific heat data suggest the coexistence of an AF order and a partial magnetic disorder. Neutron diffraction measurements reveal that the coexisted state is formed instead of the Néel AF state that has previously been reported for conventional Li2MnO3. These results indicate that high pressure makes a breakthrough to introduce partial disorder within crystals and designs not only a unique magnetic structure but also other physical properties.

Published
2022

32. Demonstration of electric double layer gating under high pressure by the development of field-effect diamond anvil cell

Author

Adachi, Shintaro, primary, Matsumoto, Ryo, additional, Yamamoto, Sayaka, additional, Yamamoto, Takafumi D., additional, Terashima, Kensei, additional, Saito, Yoshito, additional, Esparza Echevarria, Miren, additional, Baptista de Castro, Pedro, additional, Song, Peng, additional, Iwasaki, Suguru, additional, Takeya, Hiroyuki, additional, and Takano, Yoshihiko, additional

Published
2020
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33. Element-selectively tracking ultrafast demagnetization process in Co/Pt multilayer thin films by the resonant magneto-optical Kerr effect

Author

Yamamoto, Kohei, primary, Moussaoui, Souliman El, additional, Hirata, Yasuyuki, additional, Yamamoto, Susumu, additional, Kubota, Yuya, additional, Owada, Shigeki, additional, Yabashi, Makina, additional, Seki, Takeshi, additional, Takanashi, Koki, additional, Matsuda, Iwao, additional, and Wadati, Hiroki, additional

Published
2020
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34. Determination of site occupancy of boron in 6H–SiC by multiple-wavelength neutron holography

Author

Kouichi Hayashi, Maximilian Lederer, Yohei Fukumoto, Masashi Goto, Yuta Yamamoto, Naohisa Happo, Masahide Harada, Yasuhiro Inamura, Kenichi Oikawa, Kenji Ohoyama, and Peter Wellmann

Subjects
Physics and Astronomy (miscellaneous)
Abstract

The local structure around boron doped in 6H-type silicon carbide (SiC) was investigated using neutron holography. Three-dimensional atomic images reconstructed from multiple-wavelength holograms revealed the boron substitution for both silicon and carbon. To determine boron locations accurately, we calculated holograms with varying occupancies of six different sites and fit image intensities with those obtained from experimental holograms by the steepest descent method. As a result, it was found that boron atoms were selectively located at the Si–C-cubic site layer. Furthermore, boundaries right above the boron locations were suggested from the absence of atomic images in the upper region of reconstruction.

Published
2022

35. Evaluation of degradation behavior in quantum dot light-emitting diode with different hole transport materials via transient electroluminescence

Author

Yasuhiko Arakawa, Takahiro Doe, Yusuke Sakakibara, Kazuki Goto, Masaki Yamamoto, Satoru Yamamoto, Hirohisa Yamada, Tatsuya Ryowa, Makoto Izumi, Keisuke Kitano, Masaya Ueda, and Kobashi Tadashi

Subjects
010302 applied physics, Electron mobility, Materials science, Physics and Astronomy (miscellaneous), business.industry, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Luminance, law.invention, Quantum dot, law, 0103 physical sciences, Optoelectronics, Constant current, Degradation (geology), 0210 nano-technology, business, Luminescence, Light-emitting diode, Diode
Abstract

In this study, we evaluated the degradation mechanism in quantum dot light-emitting diodes (QLEDs) to improve the device lifetime. We measured the hole mobility using the delay time of transient electroluminescence for three types of hole transport layer (HTL) materials. In addition, we estimated the degradation of luminance efficiency and hole mobility under constant current drive. As a result, the HTL material with a higher hole mobility yielded longer QLED device lifetimes. Through substitution of the HTL material from poly (9-vinylcarbazole) (PVK) to poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), the hole mobility and the 95% luminance lifetime from initial luminance improved from 0.5 × 10−5 cm2/V⋅s and 2.90 h at J = 10 mA/cm2 to 1.1 × 10−5 cm2/V⋅s and 179 h, respectively. Moreover, we clarified that the degradation of the luminescent efficiency is correlated with the hole mobility.

Published
2021

44. Diamond anvil cell with boron-doped diamond heater for high-pressure synthesis andin situtransport measurements

Author

Takeshi Sakai, Shintaro Adachi, Tetsuo Irifune, Yoshihiko Takano, Sayaka Yamamoto, and Ryo Matsumoto

Subjects
Superconductivity, In situ, Materials science, Physics and Astronomy (miscellaneous), business.industry, Annealing (metallurgy), Condensed Matter - Superconductivity, FOS: Physical sciences, Diamond, engineering.material, Epitaxy, Diamond anvil cell, Superconductivity (cond-mat.supr-con), Thermometer, engineering, Optoelectronics, business, Single crystal
Abstract

Temperature and pressure are essential parameters in the synthesis, evaluation, and application of functional materials. This study proposes the addition of a heating function to a high-pressure diamond anvil cell (DAC) with in-situ measurement probes. The proposed DAC allows for simultaneous control of temperature and pressure within the sample space and can be used to synthesize functional materials under extreme conditions. The various components, namely the heater, thermometer, and measurement probes, were fabricated with a boron-doped diamond epitaxial film and could be used repeatedly. The developed DAC was used to successfully conduct the high-pressure annealing of La(O,F)BiS$_{2}$ single crystal and the high-pressure synthesis of EuFBiS$_{2}$ superconductors. The proposed technique shows promise for further exploration of superconductors to broaden the research field.

Published
2021

45. Partial cation disorder in Li2MnO3 obtained by high-pressure synthesis.

Author

Abulikemu, Aierxiding, Gao, Shenghan, Matsunaga, Toshiyuki, Takatsu, Hiroshi, Tassel, Cédric, Kageyama, Hiroshi, Saito, Takashi, Watanabe, Toshiki, Uchiyama, Tomoki, Yamamoto, Kentaro, Uchimoto, Yoshiharu, and Takami, Tsuyoshi

Subjects
NEUTRON measurement, SPECIFIC heat, CALORIMETRY, MAGNETIC structure, NEUTRON diffraction
Abstract

While atomic disorder has provided a paradigm shift in crystalline materials because of unusual atomic arrangements and functional response, "partial" disorder is scarcely reported until now. We discovered partial cation disorder in Li2MnO3 with fewer stacking faults, which was synthesized under high pressure. Mn and Li atoms in a Mn2/3Li1/3O2 layer disorder while Li atoms in a Li layer order. Magnetization and specific heat measurements indicate a long-range antiferromagnetic (AF) order below 35 K. The irreversibility observed in the magnetization data and the hump observed for the specific heat data suggest the coexistence of an AF order and a partial magnetic disorder. Neutron diffraction measurements reveal that the coexisted state is formed instead of the Néel AF state that has previously been reported for conventional Li2MnO3. These results indicate that high pressure makes a breakthrough to introduce partial disorder within crystals and designs not only a unique magnetic structure but also other physical properties. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Reversible thermally controlled spontaneous magnetization switching in perovskite-type manganite

Author

Yamamoto, Hajime, primary, Sekikawa, Satoru, additional, Taniguchi, Haruka, additional, Matsukawa, Michiaki, additional, Shigematsu, Kei, additional, Honda, Takashi, additional, Yamauchi, Kunihiko, additional, Ikeda, Kazutaka, additional, Otomo, Toshiya, additional, Sakakura, Terutoshi, additional, Azuma, Masaki, additional, Nimori, Shigeki, additional, Noda, Yukio, additional, and Kimura, Hiroyuki, additional

Published
2020
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49. Element-selectively tracking ultrafast demagnetization process in Co/Pt multilayer thin films by the resonant magneto-optical Kerr effect

Author

Shigeki Owada, Kohei Yamamoto, Makina Yabashi, Iwao Matsuda, Susumu Yamamoto, Hiroki Wadati, Takeshi Seki, Koki Takanashi, Yasuyuki Hirata, Souliman El Moussaoui, and Yuya Kubota

Subjects
010302 applied physics, Condensed Matter - Materials Science, Magnetization dynamics, Kerr effect, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Demagnetizing field, Free-electron laser, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Magneto-optic Kerr effect, Ferromagnetism, 0103 physical sciences, Atom, Thin film, 0210 nano-technology
Abstract

We examined the photo-induced dynamics of ferromagnetic Co/Pt thin films demonstrating perpendicular magnetic anisotropy with element specificity using resonant polar magneto-optical Kerr effect measurements at Pt~N${}_{6,7}$ and Co~M${}_{2,3}$ edges with an x-ray free electron laser. The obtained results showed a clear element dependence of photo-induced demagnetization time scales: $\tau_\textrm{demag.}^\textrm{Co}=80\pm60~\textrm{fs}$ and $\tau_\textrm{demag.}^\textrm{Pt}=640\pm140~\textrm{fs}$. This dependence is explained by the induced moment of the Pt atom by current flow from the Co layer through the interfaces. The observed magnetization dynamics of Co and Pt can be attributed to the characteristics of photo-induced Co/Pt thin film phenomena including all-optical switching.

Published
2020

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