Kay Yakushiji

National Institute of Advanced Industrial Science and Technology

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Shinji Yuasa

National Institute of Advanced Industrial Science and Technology

234

Hitoshi Kubota

Kyocera (United States)

218

Akio Fukushima

National Institute of Advanced Industrial Science and Technology

214

Sumito Tsunegi

National Institute of Advanced Industrial Science and Technology

Takayuki Nozaki

National Institute of Advanced Industrial Science and Technology

Shingo Tamaru

National Institute of Advanced Industrial Science and Technology

Yoshishige Suzuki

Osaka University

Vincent Cros

Centre National de la Recherche Scientifique

Julie Grollier

Centre National de la Recherche Scientifique

Kōki Takanashi

Tohoku University

Cooperative Institutions

National Institute of Advanced Industrial Science and Technology

123

Tohoku University

Centre National de la Recherche Scientifique

Osaka University

The University of Tokyo

Japan Science and Technology Agency

Laboratoire Albert Fert

Université Paris-Saclay

Université Paris-Sud

Spintronics Research Network of Japan

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Low Gilbert damping in epitaxial thin films of the nodal-line semimetal D03−Fe3Ga

Physical review. B./Physical review. B (2021)

Shoya Sakamoto Tomoya Higo Shingo Tamaru Hitoshi Kubota Kay Yakushiji

$D{0}_{3}$-ordered ${\mathrm{Fe}}_{3}\mathrm{Ga}$ has been recently reported to show a giant anomalous Nernst effect due to a large Berry curvature along the interconnected nodal lines concentrated near the Fermi level. This peculiar band structure may be advantageous for spintronics device applications because one can expect a strong response to a gate-voltage application. This study evaluates the Gilbert damping constants, a key parameter governing the magnetization dynamics of epitaxial thin films of $D{0}_{3}\text{\ensuremath{-}}{\mathrm{Fe}}_{3}\mathrm{Ga}$ and bcc-Fe by ferromagnetic resonance measurements. We find that the Gilbert damping constant of $D{0}_{3}\text{\ensuremath{-}}{\mathrm{Fe}}_{3}\mathrm{Ga} [(6.0\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}]$ is relatively low and comparable to that of Fe $[(2.3\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}]$. The low Gilbert damping suggests that the interconnected nodal lines near the Fermi level do not hinder magnetization dynamics, making $D{0}_{3}\text{\ensuremath{-}}{\mathrm{Fe}}_{3}\mathrm{Ga}$ even more attractive as a building block of spintronics devices.

10.1103/physrevb.103.165122

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Citations (6)

Low-Energy Truly Random Number Generation with Superparamagnetic Tunnel Junctions for Unconventional Computing

Physical Review Applied (2017)

Damir Vodenicarevic Nicolas Locatelli A. Mizrahi Joseph S. Friedman Adrien F. Vincent

Random number generation is critical for many emerging computing schemes, but the associated energy consumption and circuit area are major bottlenecks. This study exploits the stochastic behavior of superparamagnetic tunnel junctions, magnetic nanodevices that, due solely to thermal noise, will switch randomly between two well-defined states. These tunnel junctions can produce high-quality, truly random bit streams, with an energy efficiency that is orders of magnitude better than the state of the art. The authors furthermore develop an example that highlights the utility of superparamagnetic random number generation for low-energy probabilistic computing.

Superparamagnetism

10.1103/physrevapplied.8.054045

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Citations (158)

The Chiral Splitting of Spin Wave Eigen Modes in the 120-nm-radius FeB Disk Shaped Nano-magnet

Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials (2016)

J. Cho Shinji Miwa Kay Yakushiji Shingo Tamaru Hitoshi Kubota

10.7567/ssdm.2016.g-1-04

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Citations (0)

Efficient excitation of ferromagnetic resonance for radio-frequency amplification in magnetic tunnel junctions

The Japan Society of Applied Physics (2017)

Minori Goto Yosuke Wakatake U.K. Oji Shinji Miwa Hitoshi Kubota

Tunnel magnetoresistance

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Stability of out-of-plane precession with the application of a tilted magnetic field in spin torque oscillator having a planar free layer and a perpendicular polarizer

The Japan Society of Applied Physics (2016)

Ryo Hiramatsu Hitoshi Kubota Sumito Tsunegi Shingo Tamaru Kay Yakushiji

Polarizer

Precession

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Magneto-transport properties in perpendicularly magnetized magnetic tunnel junctions using an Mg40Fe10O50 tunnel barrier

Acta Materialia (2024)

Tatsuya Yamamoto Tomohiro Ichinose Jun Uzuhashi Takayuki Nozaki T. Ohkubo

Tunnel magnetoresistance

Magneto

Tunnel junction

10.1016/j.actamat.2024.119749

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Citations (2)

A magnetic synapse: multilevel spin-torque memristor with perpendicular anisotropy

Scientific Reports (2016)

Steven Lequeux J. Sampaio Vincent Cros Kay Yakushiji Akio Fukushima

Abstract Memristors are non-volatile nano-resistors which resistance can be tuned by applied currents or voltages and set to a large number of levels. Thanks to these properties, memristors are ideal building blocks for a number of applications such as multilevel non-volatile memories and artificial nano-synapses, which are the focus of this work. A key point towards the development of large scale memristive neuromorphic hardware is to build these neural networks with a memristor technology compatible with the best candidates for the future mainstream non-volatile memories. Here we show the first experimental achievement of a multilevel memristor compatible with spin-torque magnetic random access memories. The resistive switching in our spin-torque memristor is linked to the displacement of a magnetic domain wall by spin-torques in a perpendicularly magnetized magnetic tunnel junction. We demonstrate that our magnetic synapse has a large number of intermediate resistance states, sufficient for neural computation. Moreover, we show that engineering the device geometry allows leveraging the most efficient spin torque to displace the magnetic domain wall at low current densities and thus to minimize the energy cost of our memristor. Our results pave the way for spin-torque based analog magnetic neural computation.

Memristor

Memistor

Neuromorphic engineering

Domain wall (magnetism)

Tunnel magnetoresistance

Spin-transfer torque

10.1038/srep31510

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Citations (224)

Cryogenic Temperature Deposition of High-Performance CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on ϕ300 mm Wafers

ACS Applied Electronic Materials (2023)

Tomohiro Ichinose Tatsuya Yamamoto Takayuki Nozaki Kay Yakushiji Shingo Tamaru

We developed a cryogenic temperature deposition process for high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) on ϕ300 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 was investigated in detail. When CoFeB was deposited at 100 K, the MTJs exhibited a perpendicular magnetic anisotropy (PMA) of 214 μJ/m2 and a voltage-controlled magnetic anisotropy (VCMA) coefficient of −45 fJ/V m, 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. A cryogenic temperature sputtering deposition is expected to be a standard manufacturing process for next-generation magnetoresistive random-access memory.

Tunnel magnetoresistance

Deposition

10.1021/acsaelm.3c00068

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Citations (7)

High domain wall velocities via spin transfer torque using vertical current injection

Scientific Reports (2013)

Peter J. Metaxas J. Sampaio André Chanthbouala Rie Matsumoto A. Anane

Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm2. Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching.

Domain wall (magnetism)

Spin-transfer torque

Position (finance)

10.1038/srep01829

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Citations (43)

Spin-dependent Single Electron Tunneling and Spin Accumulation in Nonmagnetic Nanoparticles

한국자기학회 학술연구발표회 논문개요집 (2007)

Seiji Mitani Yuta Nogi H. Wang F. Ernult Kay Yakushiji

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