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137 results on '"Tamaru, Shingo"'

2. Interfacial Fe segregation and its influence on magnetic properties of CoFeB/MgFeO multilayers

Author

Ichinose, Tomohiro, Yamamoto, Tatsuya, Nozaki, Takayuki, Yakushiji, Kay, Tamaru, Shingo, and Yuasa, Shinji

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We investigated the effect of Fe segregated from partially Fe-substituted MgO (MgFeO) on the magnetic properties of CoFeB/MgFeO multilayers. X-ray photoelectron spectroscopy (XPS) as well as magnetic measurements revealed that the segregated Fe was reduced to metal and exhibited ferromagnetism at the CoFeB/MgFeO interface. The CoFeB/MgFeO multilayer showed more than 2-fold enhancement in perpendicular magnetic anisotropy (PMA) energy density compared with a standard CoFeB/MgO multilayer. The PMA energy density was further enhanced by inserting an ultrathin MgO layer in between CoFeB and MgFeO layers. Ferromagnetic resonance measurement also revealed a remarkable reduction of magnetic damping in the CoFeB/MgFeO multilayers., Comment: 15 pages, 5 figures

Published
2023

3. Cryogenic temperature deposition of high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions on 300 mm wafers

Author

Ichinose, Tomohiro, Yamamoto, Tatsuya, Nozaki, Takayuki, Yakushiji, Kay, Tamaru, Shingo, Konoto, Makoto, and Yuasa, Shinji

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We developed a cryogenic temperature deposition process for high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) on 300 mm thermally oxidized silicon wafers. The effect of the deposition temperature of the CoFeB layers on the nanostructure, magnetic and magneto-transport properties of the MTJs were investigated in detail. When CoFeB was deposited at 100 K, the MTJs exhibited a perpendicular magnetic anisotropy (PMA) of 214 uJ/m2 and a voltage-controlled magnetic anisotropy (VCMA) coefficient of -45 fJ/Vm, corresponding to 1.4- and 1.7-fold enhancements in PMA and VCMA, respectively, compared to the case of room-temperature deposition of CoFeB. The improvement in the MTJ properties was not simply due to the morphology of the MTJ films. The interface-sensitive magneto-transport properties indicated that interfacial qualities such as intermixing and oxidation states at the MgO/CoFeB interfaces were improved by the cryogenic temperature deposition. Cryogenic-temperature sputtering deposition is expected to be a standard manufacturing process for next-generation magnetoresistive random-access memory., Comment: Submitted to ACS Applied Materials and Interfaces

Published
2023

9. Role of Magnetic Field in Self-Oscillation of Nanomagnet Excited by Spin Torque

Author

Taniguchi, Tomohiro, Tamaru, Shingo, Arai, Hiroko, Tsunegi, Sumito, Kubota, Hitoshi, and Imamura, Hiroshi

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The critical current of the self-oscillation of spin torque oscillator (STO) consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer was studied by solving the Landau-Lifshitz-Gilbert (LLG) equation. We found that the critical current diverged at certain field directions, indicating that the self-oscillation does not occur at these directions. It was also found that the sign of the critical current changed depending on the applied field direction., Comment: 4 pages, 3 figures, conference proceeding of Intermag 2014

Published
2014
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10. Critical Field of Spin Torque Oscillator with Perpendicularly Magnetized Free Layer

Author

Taniguchi, Tomohiro, Arai, Hiroko, Tsunegi, Sumito, Tamaru, Shingo, Kubota, Hitoshi, and Imamura, Hiroshi

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The oscillation properties of a spin torque oscillator consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer are studied based on an analysis of the energy balance between spin torque and damping. The critical value of an external magnetic field applied normal to the film plane is found, below which the controllable range of the oscillation frequency by the current is suppressed. The value of the critical field depends on the magnetic anisotropy, the saturation magnetization, and the spin torque parameter., Comment: 5 pages, 4 figures

Published
2013
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12. List of contributors

Author

Elphick, Kelvin, primary, Fischer, Peter, additional, Frost, William, additional, Fujita, Takayuki, additional, Fukami, Shunsuke, additional, Fukushima, Akio, additional, Handa, Hiroshi, additional, Hatano, Mutsuko, additional, Hillebrands, Burkard, additional, Hirohata, Atsufumi, additional, Horii, Kazuyoshi, additional, Irino, Tomoyuki, additional, Ishiguro, Yuto, additional, Ishihara, Tomoko, additional, Ishikawa, Noriaki, additional, Jędryka, Ewa, additional, Jeyadevan, Balachandran, additional, Kakuta, Masaya, additional, Kanda, Kensuke, additional, Kerber, Nico, additional, Kitamoto, Yoshitaka, additional, Kläui, Mathias, additional, Kohno, Hiroshi, additional, Kubota, Hitoshi, additional, Kubota, Takahide, additional, Kudo, Takahiro, additional, Kusakabe, Moriaki, additional, Kuwahata, Akihiro, additional, Lee, Dong-Kyu, additional, Lee, Kyung-Jin, additional, Mamiya, Hiroaki, additional, Marnitz, Luca, additional, Matsuda, Sachiko, additional, Mizuguchi, Masaki, additional, Moskaltsova, Anastasiia, additional, Murata, Keita, additional, Nakane, Jotaro J., additional, Nakatani, Yoshinobu, additional, Nowak, Ulrich, additional, Ogasawara, Takeshi, additional, Ogawa, Toru, additional, Ohkochi, Takuo, additional, Onishi, Tatsuya, additional, Ono, Teruo, additional, Oogane, Mikihiko, additional, Oura, Masaki, additional, Polewczyk, Vincent, additional, Ramos, Rafael, additional, Reiss, Günter, additional, Saito, Yoshiaki, additional, Saitoh, Eiji, additional, Sato, Nana, additional, Schmalhorst, Jan-Michael, additional, Seki, Takeshi, additional, Sekiguchi, Koji, additional, Sekino, Masaki, additional, Stadler, Bethanie J.H., additional, Sukegawa, Hiroaki, additional, Suzuki, Motohiro, additional, Takanashi, Koki, additional, Tamaru, Shingo, additional, Tashiro, Kunihisa, additional, Tatara, Gen, additional, Tomita, Satoshi, additional, Ueda, Tetsuya, additional, Ueno, Toshiyuki, additional, Vaz, Carlos A.F., additional, Wakiwaka, Hiroyuki, additional, Weißenhofer, Markus, additional, Wójcik, Marek, additional, Yabukami, Shin, additional, Yamada, Keisuke, additional, Yamaguchi, Akinobu, additional, Yanagihara, Hideto, additional, and Zamani Kouhpanji, Mohammad Reza, additional

Published
2021
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15. Improvement in perpendicular magnetic anisotropy and its voltage control efficiency in CoFeB/MgO tunnel junctions with Ta/Mo layered adhesion structures.

Author

Ichinose, Tomohiro, Yamamoto, Tatsuya, Uzuhashi, Jun, Nozaki, Takayuki, Ohkubo, Tadakatsu, Yakushiji, Kay, Tamaru, Shingo, Hono, Kazuhiro, and Yuasa, Shinji

Abstract

By utilizing Ta/Mo layered adhesion structures, thermally robust perpendicular magnetic anisotropy and voltage-controlled magnetic anisotropy (VCMA) effects were achieved in magnetic tunnel junctions (MTJs) with ultrathin CoFeB films grown on MgO. After annealing at 400 °C, MTJs with Ta/Mo layered adhesion exhibited VCMA coefficients of 48 fJ/Vm. The combination of Ta and Mo improved the crystalline orientation and flatness of the CoFeB/MgO tunneling barrier interfaces, as determined by cross-sectional scanning transmission electron microscopy. Additionally, we demonstrate that the small interdiffusion between Mo and CoFe enables effective scavenging of B from CoFeB by increasing the thickness of the B sink layer without impairing the device performance due to atomic diffusion. [ABSTRACT FROM AUTHOR]

Published
2022
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34. Large voltage-induced coercivity change in Pt/Co/CoO/amorphous TiOx structure and heavy metal insertion effect.

Author

Nozaki, Tomohiro, Tamaru, Shingo, Konoto, Makoto, Nozaki, Takayuki, Kubota, Hitoshi, Fukushima, Akio, and Yuasa, Shinji

Subjects
*PERPENDICULAR magnetic anisotropy, *COERCIVE fields (Electronics), *INFORMATION storage & retrieval systems, *DEGREES of freedom, *PERMITTIVITY, *HEAVY metals
Abstract

There is urgent need for spintronics materials exhibiting a large voltage modulation effect to fulfill the great demand for high-speed, low-power-consumption information processing systems. Fcc-Co (111)-based systems are a promising option for research on the voltage effect, on account of their large perpendicular magnetic anisotropy (PMA) and high degree of freedom in structure. Aiming to observe a large voltage effect in a fcc-Co (111)-based system at room temperature, we investigated the voltage-induced coercivity (Hc) change of perpendicularly magnetized Pt/heavy metal/Co/CoO/amorphous TiOx structures. The thin CoO layer in the structure was the result of the surface oxidation of Co. We observed a large voltage-induced Hc change of 20.2 mT by applying 2 V (0.32 V/nm) to a sample without heavy metal insertion, and an Hc change of 15.4 mT by applying 1.8 V (0.29 V/nm) to an Ir-inserted sample. The relative thick Co thickness, Co surface oxidation, and large dielectric constant of TiOx layer could be related to the large voltage-induced Hc change. Furthermore, we demonstrated the separate adjustment of Hc and a voltage-induced Hc change by utilizing both upper and lower interfaces of Co. [ABSTRACT FROM AUTHOR]

Published
2021
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40. Spin torque diode effect of the magnetic tunnel junction with MnGa free layer

Author

Tsunegi, Sumito, primary, Mizunuma, Kotaro, additional, Suzuki, Kazuya, additional, Imamura, Hiroshi, additional, Tamaru, Shingo, additional, Yoshimura, Masahiro, additional, Sato, Masashige, additional, Kono, Yasushi, additional, Wado, Hiroyuki, additional, Fukushima, Akio, additional, Kubota, Hitoshi, additional, and Mizukami, Shigemi, additional

Published
2018
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42. Highly efficient voltage control of spin and enhanced interfacial perpendicular magnetic anisotropy in iridium-doped Fe/MgO magnetic tunnel junctions

Author

Nozaki, Takayuki, primary, Kozioł-Rachwał, Anna, additional, Tsujikawa, Masahito, additional, Shiota, Yoichi, additional, Xu, Xiandong, additional, Ohkubo, Tadakatsu, additional, Tsukahara, Takuya, additional, Miwa, Shinji, additional, Suzuki, Motohiro, additional, Tamaru, Shingo, additional, Kubota, Hitoshi, additional, Fukushima, Akio, additional, Hono, Kazuhiro, additional, Shirai, Masafumi, additional, Suzuki, Yoshishige, additional, and Yuasa, Shinji, additional

Published
2017
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45. Spin-wave eigenmodes in single disk-shaped FeB nanomagnet

Author

Cho, Jaehun, primary, Miwa, Shinji, additional, Yakushiji, Kay, additional, Tamaru, Shingo, additional, Kubota, Hitoshi, additional, Fukushima, Akio, additional, Fujimoto, Satoshi, additional, Tamura, Eiiti, additional, You, Chun-Yeol, additional, Yuasa, Shinji, additional, and Suzuki, Yoshishige, additional

Published
2016
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