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Yamanouchi, Michihiko*; Araki, Yasufumi; Sakai, Takaki*; Uemura, Tetsuya*; Ota, Hiromichi*; Ieda, Junichi
Science Advances (Internet), 8(15), p.eabl6192_1 - eabl6192_6, 2022/04
Times Cited Count:5 Percentile:75.68(Multidisciplinary Sciences)In a ferromagnetic Weyl metal SrRuO, a large effective magnetic field exerted on a magnetic domain wall (DW) by current has been reported. We show that the ratio of to current density exhibits nonmonotonic temperature dependence and surpasses those of conventional spin-transfer torques and spin-orbit torques. This enhancement is described well by topological Hall torque (THT), which is exerted on a DW by Weyl electrons emerging around Weyl points when an electric field is applied across the DW. The ratio of the arising from the THT to current density is over one order of magnitude higher than that originating from spin-transfer torques and spin-orbit torques reported in metallic systems, showing that the THT may provide a better way for energy-efficient manipulation of magnetization in spintronics devices.
Yamanouchi, Michihiko*; Oyamada, Tatsuro*; Sato, Koichi*; Ota, Hiromichi*; Ieda, Junichi
IEEE Transactions on Magnetics, 55(7), p.1400604_1 - 1400604_4, 2019/07
Times Cited Count:4 Percentile:27.86(Engineering, Electrical & Electronic)Tomizawa, Hiromitsu*; Sato, Takahiro*; Ogawa, Kanade*; Togawa, Kazuaki*; Tanaka, Takatsugu*; Hara, Toru*; Yabashi, Makina*; Tanaka, Hitoshi*; Ishikawa, Tetsuya*; Togashi, Tadashi*; et al.
High Power Laser Science and Engineering, 3, p.e14_1 - e14_10, 2015/04
Times Cited Count:6 Percentile:34.58(Optics)no abstracts in English
Itakura, Ryuji; Hosaka, Koichi*; Yokoyama, Atsushi; Ikuta, Tomoya*; Kannari, Fumihiko*; Yamanouchi, Kaoru*
Progress in Ultrafast Intense Laser Science XI; Springer Series in Chemical Physics, Vol.109, p.23 - 42, 2015/00
We investigate the multichannel dissociative ionization of ethanol in intense laser fields by the photoelectron-photoion coincidence momentum imaging and identify separately the ionization and subsequent electronic excitation in ethanol. From the energy correlation between a photoelectron and a fragment ion, we reveal the amount of the internal energy gained by ethanol cations from the laser field varies depending on the respective ionization and electronic excitation pathways.
Kim, J.*; Sinha, J.*; Mitani, Seiji*; Hayashi, Masamitsu*; Takahashi, Saburo*; Maekawa, Sadamichi; Yamanouchi, Michihiko*; Ohno, Hideo*
Physical Review B, 89(17), p.174424_1 - 174424_8, 2014/05
Times Cited Count:88 Percentile:94.07(Materials Science, Multidisciplinary)We have studied the underlayer thickness and temperature dependencies of the current-induced effective field in CoFeB/MgO heterostructures with Ta-based underlayers. The underlayer thickness at which the effective field saturates is found to be different between the two orthogonal components of the effective field; i.e., the dampinglike term tends to saturate at a smaller underlayer thickness than the fieldlike term. For large underlayer thickness films in which the effective field saturates, we find that the measurement temperature significantly influences the size of the effective field. A striking difference is found in the temperature dependence of the two components: the dampinglike term decreases whereas the fieldlike term increases with increasing temperature. Using a simple spin diffusion-spin transfer model, we find that all of these results can be accounted for provided the real and imaginary parts of an effective spin mixing conductance are negative. These results imply that either spin transport in this system is different from conventional metallic interfaces or effects other than spin diffusion into the magnetic layer need to be taken into account in order to model the system accurately.
Yabashi, Makina*; Tanaka, Hitoshi*; Tanaka, Takashi*; Tomizawa, Hiromitsu*; Togashi, Tadashi*; Nagasono, Mitsuru*; Ishikawa, Tetsuya*; Harries, J.; Hikosaka, Yasumasa*; Hishikawa, Akiyoshi*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164001_1 - 164001_19, 2013/08
Times Cited Count:71 Percentile:95.24(Optics)Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Togashi, Tadashi*; Fukami, Kenji*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164006_1 - 164006_6, 2013/08
Times Cited Count:3 Percentile:19.12(Optics)By introducing 13th- (61.7 nm) and 15th-order harmonics (53.4 nm) of femtosecond laser pulses at 800 nm into an undulator of SCSS (SPring-8 Compact SASE Source) test accelerator at RIKEN, these harmonic pulses were amplified by a factor of more than 10 with a high contrast ratio through the interaction between accelerated electron bunches and the harmonic pulses. From numerical simulations of the amplification processes of high-order harmonic pulses in the undulator, optimum conditions of the electron bunch duration interacting with the high-order harmonic pulses were investigated for generating full-coherent and intense pulses in the extreme ultraviolet wavelength region.
Ogawa, Kanade*; Sato, Takahiro*; Matsubara, Shinichi*; Okayasu, Yuichi*; Togashi, Tadashi*; Watanabe, Takahiro*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; et al.
Proceedings of 10th Conference on Lasers and Electro-Optics Pacific Rim and 18th OptoElectronics and Communications Conference and Photonics in Switching 2013 (CLEO-PR & OECC/PS 2013) (USB Flash Drive), 2 Pages, 2013/06
no abstracts in English
Hosaka, Koichi*; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Itakura, Ryuji
Journal of Chemical Physics, 138(20), p.204301_1 - 204301_9, 2013/05
Times Cited Count:15 Percentile:50.42(Chemistry, Physical)Dissociative ionization of ethanol (CHOH) induced by an intense near-infrared laser pulse are investigated using photoelectron-photoion coincidence method. It is shown that both the electronic ground state and the first electronically excited state of CHOH are produced at the moment of photoelectron emission. From the observed correlation between the electronic states of CHOH prepared at the moment of photoelectron emission and the kinetic energy release of the fragment ions, it is revealed that CHOH prepared in the electronic ground state at the photoelectron emission gains larger internal energy in the end than that prepared in the electronically excited state. The averaged internal energy of CHOH just before the dissociation is found to increase when the laser field intensity increases from 9 to 23 TW/cm. And when the laser pulse duration increases from 35 to 800 fs.
Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Hara, Toru*; et al.
Proceedings of Ultrafast Optics IX (CD-ROM), 2 Pages, 2013/03
We have demonstrated free-electron laser radiation seeded by high-order harmonics in the extreme-ultraviolet region. Strong enhancement of the radiation intensity by a factor of 104 was observed with timing control of an electro-optical sampling technique.
Iwasaki, Atsushi*; Sato, Takahiro*; Owada, Shigeki*; Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Kannari, Fumihiko*; Yagishita, Akira*; et al.
Reza Kenkyu, 40(9), p.687 - 690, 2012/09
no abstracts in English
Iwasaki, Atsushi*; Sato, Takahiro*; Owada, Shigeki*; Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Matsubara, Shinichi*; Okayasu, Yuichi*; et al.
Proceedings of International Conference on Ultrafast Phenomena 2012 (UP 2012) (Internet), 3 Pages, 2012/07
Times Cited Count:0 Percentile:0.03no abstracts in English
Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Hara, Toru*; et al.
Proceedings of 11th International School and Symposium on Synchrotron Radiation in Natural Science (ISSRNS 2012), p.1 - 21, 2012/05
The 13th harmonic of a Ti:sapphire laser has been significantly amplified with the SCSS test accelerator. The temporal and spatial overlap of the electron beam and the high harmonic radiation were precisely tuned for achieving the seeded free electron laser operation. With numerical simulation the present HH-seeded FEL scheme could readily be applied to the wavelength region down to 10 nm.
Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Itakura, Ryuji
Journal of Physics B; Atomic, Molecular and Optical Physics, 44(19), p.191002_1 - 191002_5, 2011/10
Times Cited Count:10 Percentile:47.26(Optics)Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.318 TW/cm) are separately investigated by measuring in coincidence an electron and a product ion produced from CHOH. We reveal that the nascent population in the electronically excited CHOH prepared by the ionization decreases as the laser intensity increases, while the subsequent electronic excitation is enhanced through the resonant electronic transitions. Ionization and electronic excitation mechanisms are described based on the electronic state distributions of CHOH.
Sato, Takahiro*; Iwasaki, Atsushi*; Ishibashi, Kazuki*; Okino, Tomoya*; Yamanouchi, Kaoru*; Adachi, Junichi*; Yagishita, Akira*; Yazawa, Hiroki*; Kannari, Fumihiko*; Aoyama, Makoto; et al.
Europhysics News, 42(5), P. 10, 2011/09
The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4-61.4 nm) covering the 1s-2p and 1s-3p resonant transitions of He. On the basis of the dependences of the yield of He on the XUV light-field intensity at 53.4, 58.4, 56.0 and 61.4 nm, the absolute values of the two-photon ionization cross sections of He at the four different wavelengths and their dependence on the light-field intensity were determined for the first time.
Sato, Takahiro*; Iwasaki, Atsushi*; Ishibashi, Kazuki*; Okino, Tomoya*; Yamanouchi, Kaoru*; Adachi, Junichi*; Yagishita, Akira*; Yazawa, Hiroki*; Kannari, Fumihiko*; Aoyama, Makoto; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 44(16), p.161001_1 - 161001_5, 2011/08
Times Cited Count:35 Percentile:82.86(Optics)The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4-61.4 nm) covering the 1s-2p and 1s-3p resonant transitions of He. On the basis of the dependences of the yield of He on the XUV light-field intensity at 53.4, 58.4, 56.0 and 61.4 nm, the absolute values of the two-photon ionization cross sections of He at the four different wavelengths and their dependence on the light-field intensity were determined for the first time.
Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Okino, Tomoya*; Yamanouchi, Kaoru*; Hara, Toru*; et al.
Proceedings of 2011 Conference on Lasers and Electro-Optics (CLEO 2011) (CD-ROM), p.1527 - 1528, 2011/05
We succeeded in generating the seeded free electron laser (FEL) with wavelengths of 61 nm at the SCSS test accelerator. The 13th (61 nm) harmonics generated by focusing the high peak power Ti:Sapphire laser to the Xe gas cell was directed to the undulator. This is first realization of the seeded FEL in extreme ultraviolet region.
Takahashi, Eiji*; Togashi, Tadashi*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Hara, Toru*; et al.
Proceedings of European Conference on Lasers and Electro-Optics and the 12th European Quantum Electronics Conference (CLEO/Europe-EQEC 2011) (CD-ROM), 1 Pages, 2011/05
We succeeded in generating the seeded free electron laser (FEL) with wavelengths of 61 nm at the SCSS test accelerator. The 13th (61 nm) harmonics generated by focusing the high peak power Ti:Sapphire laser to the Xe gas cell was directed to the undulator. This is first realization of the seeded FEL in extreme ultraviolet region.
Takahashi, Eiji*; Togashi, Tadashi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Hara, Toru*; Matsubara, Shinichi*; et al.
Proceedings of International Quantum Electronics Conference and the Pacific Rim Conference on Lasers and Electro-Optics (IQEC/CLEO Pacific Rim 2011) (CD-ROM), p.199 - 200, 2011/05
We succeeded in generating the seeded free electron laser (FEL) with wavelengths of 61 nm at the SCSS test accelerator. The 13th (61 nm) harmonics generated by focusing the high peak power Ti:Sapphire laser to the Xe gas cell was directed to the undulator. This is first realization of the seeded FEL in extreme ultraviolet region.
Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Okino, Tomoya*; Yamanouchi, Kaoru*; et al.
Optics Express (Internet), 19(1), p.317 - 324, 2011/01
Times Cited Count:93 Percentile:96.48(Optics)The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as a seeding source to a 250-MeV free-electron-laser (FEL) amplifier. When the amplification conditions were fulfilled, strong enhancement of the radiation intensity by a factor of 650 was observed. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission (SASE) based FEL radiation without the seeding source, were found to be suppressed drastically to form to a narrow-band, single peak profile at 61.2 nm. The properties of the seeded FEL radiation were well reproduced by numerical simulations. We discuss the future precept of the seeded FEL scheme to the shorter wavelength region.