Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yuichiro Kurokawa Last modified date:2021.10.28

Assistant Professor / Department of Electronics / Faculty of Information Science and Electrical Engineering

1. Yuki Hamada, Yuichiro Kurokawa, Tomoki Yamauchi, Hiroki Hanamoto, and Hiromi Yuasa, Anomalous Nernst effect in Fe–Si alloy films, Appl. Phys. Lett., 10.1063/5.0062637, 119, 152404, 119, 152404 (2021), 2021.10.
2. Carmen Martín Valderrama, Mikel Quintana, Ane Martínez de Guereñu, Tomoki Yamauchi, Yuki Hamada, Yuichiro Kurokawa, Hiromi Yuasa, Andreas Berger, Insertion layer magnetism detection and analysis using transverse magneto-optical Kerr effect (T-MOKE) ellipsometry, Journal of Physics D: Applied Physics,, 54, 54 (2021) 435002, 2021.06.
3. Chuhan Liu, Yuichiro Kurokawa, Naoki Hashimoto, Shu Horiike, Terumitsu Tanaka, Hiromi Yuasa, Spin Transfer Torque Oscillation in Orthogonal Magnetization Disks, IEEE Transactions on Magnetics, 10.1109/TMAG.2021.3084608, Early Access, 2021.05.
4. Keisuke Yamada, Shinya Masaki, Mikiya Yamamoto, Keita Kondo, Yuichiro Kurokawa, Yoichi Shiota, Takahiro Moriyama, Teruo Ono, Hiromi Yuasa, Mutsuhiro Shima, Change of longitudinal spin Seebeck voltage with annealing in Y3Fe5O12 films formed by densely packed nanocrystals, Journal of Magnetism and Magnetic Materials,, 535, 168093, 535, 168093, 2021.05.
5. Naoki Hashimoto, Shuu Horiike, Yuichiro Kurokawa, Terumitsu Tanaka, Po-Chun Chang, Wen-Chin Lin, Hiromi Yuasa, Direct observation of magnetic process in quasi-antiferromagnet by high-resolution Kerr microscopy, Japanese Journal of Applied Physics,, 60, SBBI05, 60, SBBI05, 2021.03.
6. Takumi Niimura, Yuichiro Kurokawa, Shu Horiike, Houlin Li, Hiroki Hanamoto, Ramon Weber, Andreas Berger, and Hiromi Yuasa, Influence of interface layer insertion on the spin Seebeck effect and the spin Hall magnetoresistance of Y3Fe5O12/Pt bilayer systems, PHYSICAL REVIEW B,, 102, 094411, 2020.09, We observe significantly enhanced spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) values by inserting 0.3–0.6-nm-thick layers of magnetic materials with different composition (Cr, Ni80Fe20, Co90Fe10, Fe50Co50, and Fe) at the Y3Fe5O12/Pt interface. To study the actual magnetic state of these insertion layers, we, then, investigated the magnetization of these layers via generalized magneto-optical ellipsometry. Magnetic insertion layers in this thickness range did not exhibit a measurable magnetization, even though our method should have detected even a small fraction of the bulk magnetization value for the utilized materials easily. Therefore, the observed SSE and SMR enhancement generated by the insertion of thin magnetic material layers did not result from a net interface magnetization but might, instead, be related to the paramagnetic state of the inserted layers..
7. Houlin Li, Yuichiro Kurokawa, Takumi Niimura, Tomoki Yamauchi, Hiromi Yuasa, Composition dependence of spin Seebeck voltage in YIG/Pt100-X RuX , Pt100-X CuX , and Pt100-X (Cu0.5Ru0.5)X , Japanese journal of applied physics, 10.35848/1347-4065/ab9653, 59, 7, 2020.07.
8. Shuu Horiike, Gen Nagashima, Yuichiro Kurokawa, Yongshi Zhong, Kazuto Yamanoi, Terumitsu Tanaka, Kimihide Matsuyama, Hiromi Yuasa, Magnetic dynamics of quasi-Antiferromagnetic layer fabricated by 90° magnetic coupling, Japanese journal of applied physics, 10.7567/1347-4065/ab5d62, 59, SG, SGGI02, 2020.04.
9. Yongshi Zhong, Yuichiro Kurokawa, Gen Nagashima, Shu Horiike, Takayasu Hanashima, Daniel Schönke, Pascal Krautscheid, Robert M. Reeve, Mathias Kläui, Hiromi Yuasa, Determination of fine magnetic structure of magnetic multilayer with quasi antiferromagnetic layer by using polarized neutron reflectivity analysis, AIP Advances, 10.1063/1.5130445, 10, 1, 015323, 2020.01.
10. Gen Nagashima, Yuichiro Kurokawa, Yongshi Zhong, Shuu Horiike, Daniel Schönke, Pascal Krautscheid, Robert M. Reeve, Mathias Kläui, Yuji Inagaki, Tatsuya Kawae, Terumitsu Tanaka, Kimihide Matsuyama, Kohei Ohnishi, Takashi Kimura, Hiromi Yuasa, Quasi-antiferromagnetic multilayer stacks with 90 degree coupling mediated by thin Fe oxide spacers, Journal of Applied Physics, 10.1063/1.5117869, 126, 9, 093901, 2019.09.
11. Shilei Ding, Andrew Ross, Romain Lebrun, Sven Becker, Kyujoon Lee, Isabella Boventer, Souvik Das, Yuichiro Kurokawa, Shruti Gupta, Jinbo Yang, Gerhard Jakob, and Mathias Kläui, Interfacial Dzyaloshinskii-Moriya interaction and chiral magnetic textures in a ferrimagnetic insulator, PHYSICAL REVIEW B,, 100, 100406(R), 100, 100406(R) (2019), 2019.09, The interfacial Dzyaloshinskii-Moriya interaction (DMI) in multilayers of heavy metal and ferromagnetic metals enables the stabilization of novel chiral spin structures such as skyrmions. Magnetic insulators, on the other hand, can exhibit enhanced dynamics and properties such as lower magnetic damping and therefore it is of interest to combine the properties enabled by interfacial DMI with insulating systems. Here, we demonstrate the presence of interfacial DMI in heterostructures that include insulating magnetic layers. We use perpendicularly magnetized insulating thulium iron garnet (TmIG) films capped by the heavy metal platinum, grown on gadolinium gallium garnet (GGG) substrates, and find a surprisingly strong interfacial DMI that, combined with spin-orbit torque, results in efficient switching. The interfacial origin is confirmed through thickness-dependence measurements of the DMI, revealing the characteristic 1/thickness dependence. We combine chiral spin structures and spin-orbit torques for efficient switching and identify skyrmions that allow us to establish the GGG/TmIG interface as the possible origin of the DMI..
12. Yuichiro Kurokawa, Masakazu Wakae, Satoshi Sumi, Hiroyuki Awano, Kohei Ohnishi, Hiromi Yuasa, Spin-orbit torque-driven current-induced domain wall motion in Gd-Fe magnetic wires, Japanese Journal of Applied Physics, 10.7567/1347-4065/aafa91, 58, 3, 2019.03, We fabricated Gd-Fe/Ta/sub. and W/Gd-Fe/Ta/sub. perpendicular magnetized magnetic wires and investigated current-induced domain wall motion (CIDWM) in them. The propagation field of the Gd-Fe wires is low (∼3 mT), and the wires were found to have a low threshold current density (∼3.1 ×1010 A m-2) of CIDWM. The directions of the CIDWM in Gd-Fe/Ta and W/Gd-Fe/Ta wires are opposite to each other, indicating that the CIDWM in both wires is driven by spin-orbit torque because the spin Hall torque generated by the Ta underlayer and W cap layer oppose each other..
13. Fumiya Nakata, Takumi Niimura, Yuichiro Kurokawa, Hiromi Yuasa, Spin Seebeck voltage enhancement by Mn system metals insertion at the interface between YIG and nonmagnetic layer, Japanese Journal of Applied Physics, 10.7567/1347-4065/aafb5c, 58, 2019.01, The spin Seebeck voltage was successfully increased by IrMn or Mn insertion into the interface Y3Fe5O12 and nonmagnetic Pt and TaW with positive and negative spin Hall angle, respectively. The magnitude of the spin Seebeck coefficient |S| of the samples with IrMn and Mn were higher than that with Ru insertion, which indicates that the existence of the magnetic moment is important for the spin Seebeck coefficient. Furthermore, |S| of the samples with IrMn and Mn were higher than oxide antiferromagnetic NiO, which suggests the metallic layer insertion is effective for enlarging |S| owing to the relatively long spin diffusion length. Since the inserted IrMn and NiO take the paramagnetic states as well as Mn, it is supposed that the spin fluctuation in the paramagnetic insertion layers play an important role in enhancing the spin current..
14. Masakazu Wakae, Yuichiro Kurokawa, Hiromi Yuasa, Observation of spin-orbit torque-induced magnetization switching in Gd-Fe perpendicular magnetized wire with in-plane exchange bias field, Japanese Journal of Applied Physics, 10.7567/1347-4065/aaf877, 58, 2019.01, We fabricated a Ta/Gd-Fe/Ta and a Ta/Gd-Fe/Ir22Mn78/Co90Fe10/Ta multilayered magnetic wire and investigated spin-orbit torque current-induced magnetization switching in these wires. Magnetization switching in the Ta/Gd-Fe/Ir22Mn78/Co90Fe10/Ta multilayered magnetic wire can be observed by an electric current even if the external in-plane magnetic field is not applied at all. Moreover, we successfully observed the periodical magnetization switching in the Ta/Gd-Fe/Ir22Mn78/Co90Fe10/Ta multilayered magnetic wire in zero magnetic field. This indicates that the present wire is a promising material to realize magnetic random access memory with low power consumption..
15. Keisuke Yamada, Yuichiro Kurokawa, Kazuma Kogiso, Hiromi Yuasa, Mutsuhiro Shima, Observation of longitudinal spin seebeck voltage in YIG films chemically prepared by co-precipitation and spin coating, IEEE Transactions on Magnetics, 10.1109/TMAG.2018.2865199, 55, 2, 2019.02, Longitudinal spin Seebeck effect (LSSE) of Y3Fe5O12 (YIG) thin films chemically prepared on a Si substrate with a SiO2 surface layer has been investigated with a particular focus on its dependence on the metal (Pt or W) for the capping layer used to carry out the measurements. The YIG films are prepared by a combination of co-precipitation, spin coating, and annealing processes. The structural characterization by X-ray diffraction proves that the films are polycrystalline in a garnet phase with an average crystallite size of 34 nm. The microstructural analyses of the film surface by scanning electron microscopy and scanning probe microscopy show that the roughness Ra of the film is 31 nm. The magnetic easy axis of the YIG films is in the direction parallel to the films. We have found that the polarity of the LSSE voltage VLSSE measured with a Pt capping layer apparently differs from that observed when a W capping layer is used. The value of VLSSE increases almost linearly with increasing temperature difference Δ T independent of the choice of metal for the capping layer. The observed LSSE for the polycrystalline YIG films is one order of magnitude smaller than that reported for YIG and Bi:YIG single-crystal samples grown by metal-organic decomposition..
16. Hiroyuki Awano, Satoshi Sumi, Yuichiro Kurokawa, Do Bang, Akihiko Moribayashi, Ryogo Yoshimura, Tsukasa Asari, Magnetic Recording on the RE-TM /Pt Magnetic Wire Deposited on Nano-Imprinted Plastic Substrate, 2016 International Conference of Asian Union of Magnetics Societies, ICAUMS 2016 , 10.1109/ICAUMS.2016.8479813, 2018.10.
17. Yuichiro Kurokawa, Hiroyuki Awano, Multilayered current-induced domain wall motion in Pt/Tb-Co/Ta/Tb-Co/Pt magnetic wire, AIP ADVANCES, 10.1063/1.5017814, 8, 2, 2018.02, We fabricated a Pt (3 nm)/Tb0.28Co0.72 (4 nm)/Ta (4 nm)/Tb0.26Co0.74 (4 nm)/Pt
(3 nm) multilayered magnetic wire and investigated current-induced domain wall
motion within it.We found that the Hall resistance of the Pt/Tb-Co/Ta/Tb-Co/Pt wire
has four stable levels under a magnetic field of zero. Moreover, we observed that the
domain walls in both the upper and lower ferromagnetic layers are controlled by a
single current source. This indicates that Pt/Tb-Co/Ta/Tb-Co/Pt wire can be used in
multi-level magnetic wire memory..
18. Hiromi Yuasa, Fumiya Nakata, Ryohei Nakamura, Yuichiro Kurokawa, Spin Seebeck coefficient enhancement by using Ta50W50 alloy and YIG/Ru interface, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 10.1088/1361-6463/aaaf89, 51, 13, 2018.04.
19. Yuichiro Kurokawa, Akihiro Shibata, Hiroyuki Awano, Enhancement of spin orbit torques in a Tb-Co alloy magnetic wire by controlling its Tb composition, AIP ADVANCES, 10.1063/1.4974280, 7, 5, 2017.05.
20. Yuichiro Kurokawa, Do Bang, Hiroyuki Awano, Thermally Assisted Current-Induced Domain Wall Motion in Tb/Co Magnetic Multilayered Wire with a High Domain Wall Propagation Field, IEEE Transactions on Magnetics, 10.1109/TMAG.2017.2676086, 53, 7, 2017.07, We investigated the current-induced domain wall (DW) motion in Tb/Co multilayered wire with various substrate temperatures (Ts). The coercivity and DW propagation field of the Tb/Co multilayered film are 10 and 8 kOe, respectively. In the Tb/Co wire, the DW velocity is 2.4 m/s for a current density of 4.5 × 1011 Am2 at room temperature. At Ts = 343 K, we also found that the DW velocity is about two times higher than that at room temperature. The enhancement of DW velocity can be attributed to thermally activated creep DW motion and/or the reduction of the depinning current density..
21. @Yuichiro Kurokawa, Ryogo Yoshimura, Satoshi Sumi, Hiroyuki Awano, Thermal reduction of the threshold current density for current-induced domain wall motion in Tb-Co magnetic alloy wire, AIP ADVANCES, 10.1063/1.4979727, 7, 3, 2017.03.
22. Yuichiro Kurokawa, Masaya Kawamoto, Hiroyuki Awano, Current-induced domain wall motion attributed to spin Hall effect and Dzyaloshinsky-Moriya interaction in Pt/GdFeCo (100 nm) magnetic wire, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.07MC02, 55, 7, 2016.07.
23. Kenji Sumiyama, Minoru Yamazaki, Takeshi Yoneyama, Kohdai Suzuki, Kohji Takemura, Yuichiro Kurokawa, Takehiko Hihara, Electric and magnetic evolution in sputter-deposited FexSi1-x alloy films, Materials Transactions, 10.2320/matertrans.M2016046, 57, 6, 907-912, 2016.04.
24. Kenji Sumiyama, Yuichiro Kurokawa, Hirotaka Yamada, Minoru Yamazaki, Takehiko Hihara, Electric evolution in sputter-deposited SncSnSi1-cSn alloy films, Materials Transactions, 10.2320/matertrans.M2016029, 57, 6, 903-906, 2016.04.
25. Kenji Sumiyama, Minoru Yamazaki, Yuichiro Kurokawa, Nobuyuki Shinohara, Takehiko Hihara, Electric and magnetic evolutions in composite assemblies of Fe and Si nano-particles, Materials Transactions, 10.2320/matertrans.M2014434, 56, 3, 292-296, 2015.02.
26. Yuichiro Kurokawa, Takehiko Hihara, Electrically conductive properties of Ag/Si composite nanoparticle assembled films prepared with a plasma-gas-condensation cluster source, Japanese journal of applied physics, 10.7567/JJAP.53.110313, 53, 11, 2014.11.
27. Yuichiro Kurokawa, Takehiko Hihara, Characterization of critical volume for percolation in Sn/Si bimetallic cluster assemblies with various packing fractions, journal of the physical society of japan, 10.7566/JPSJ.83.054714, 83, 5, 2014.05.
28. Yuichiro Kurokawa, Takehiko Hihara, Ikuo Ichinose, Critical field of two-dimensional superconducting Sn1-x/Si x bimetallic composite cluster assembled films with energetic cluster impact deposition, Journal of Applied Physics, 10.1063/1.4798262, 113, 17, 2013.05.
29. Kenji Sumiyama, Satoshi Kadowaki, Yuichiro Kurokawa, Naokage Tanaka, Ryoji Katoh, Takehiko Hihara, Annealing effects on structures and morphologies of Fe/Si coreshell clusters, Materials Transactions, 10.2320/matertrans.M2012383, 54, 4, 498-504, 2013.03.
30. Yuichiro Kurokawa, Takehiko Hihara, Kenji Sumiyama, Electrical resistivity and morphology of Sn 1-x/Si x core-shell cluster network prepared by a plasma-gas-condensation cluster source, Materials Transactions, 10.2320/matertrans.M2012232, 53, 11, 1929-1932, 2012.10.
31. Kenji Sumiyama, Shogo Sawa, Dong Liang Peng, Yuichiro Kurokawa, Takeshi Yamabuchi, Takehiko Hihara, Magnetic properties of cluster/thin-film laminated hybrids of FePt and FeCo alloys, Materials Transactions, 10.2320/matertrans.M2012120, 53, 9, 1563-1570, 2012.07.
32. Yuichiro Kurokawa, Takehiko Hihara, Ikuo Ichinose, Kenji Sumiyama, Possibility of exciton mediated superconductivity in nano-sized Sn/Si core-shell clusters
A process technology towards heterogeneous material in nano-scale, Japanese journal of applied physics, 10.1143/JJAP.51.070207, 51, 7 PART 1, 2012.07.