A5008461925- Magnetic properties of thin films
- Magnetic Properties and Applications
- Particle Accelerators and Free-Electron Lasers
- Heusler alloys: electronic and magnetic properties
- Particle accelerators and beam dynamics
- ZnO doping and properties
- Gyrotron and Vacuum Electronics Research
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Advanced Memory and Neural Computing
- Laser Design and Applications
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties of Alloys
- Magneto-Optical Properties and Applications
- Lightning and Electromagnetic Phenomena
- Advanced X-ray Imaging Techniques
- Theoretical and Computational Physics
- Photonic and Optical Devices
- Thermal Analysis in Power Transmission
- Laser-Plasma Interactions and Diagnostics
- Electric Motor Design and Analysis
- Characterization and Applications of Magnetic Nanoparticles
- Laser Material Processing Techniques
- Electrical Fault Detection and Protection
- Magnetic Properties and Synthesis of Ferrites
National Institute of Advanced Industrial Science and Technology
2018-2025
National Institute for Materials Science
2016-2024
Tohoku University
2008-2023
Institute for Materials Research, Tohoku University
2015-2023
Ritsumeikan University
2022-2023
Mitsubishi Electric (Japan)
2014-2023
Osaka University
1988-2022
Nagoya Institute of Technology
2019
Saitama University
2018
International Medical Research (Germany)
2016-2017
A novel nonvolatile memory utilizing spin torque transfer magnetization switching (STS), abbreviated spin-RAM hereafter, is presented for the first time. The programmed by reversal through an interaction of a momentum-torque-transferred current and magnetic moment layers in tunnel junctions (MTJs), therefore external field unnecessary as that conventional MRAM. This new programming mode has been accomplished owing to our tailored MTJ, which oval shape 100 times 150 nm. cell based on...
We investigated the influence of heavy metal doping at Fe/MgO interface on interfacial perpendicular magnetic anisotropy (PMA) and voltage-controlled (VCMA) in tunnel junctions prepared by sputtering-based deposition. The PMA was increased tungsten a maximum intrinsic energy, Ki,0 2.0 mJ/m2 obtained. Ir led to large increase VCMA coefficient factor 4.7 compared with that for standard interface. developed technique provides an effective approach enhancing properties development spintronic devices.
We investigated the voltage-controlled magnetic anisotropy (VCMA) in an ultrathin Ir-doped Fe layer with a CoxFe1−x termination layer. The VCMA effect depends on concentration of alloy, and large coefficient, as high −350 fJ/Vm, was obtained Co-rich First principles calculations revealed that increased is due not only to added Co atoms but also Ir adjacent atoms. Interface engineering using CoFe effective for recovering tunneling magnetoresistance while maintaining effect. developed...
We study characteristics of CoFeB-MgO magnetic tunnel junction with perpendicular easy-axis (p-MTJ) at a reduced dimension down to 1X nm fabricated by hard-mask process. p-MTJ double-interface shows higher thermal stability than that single-interface. Thermal factor 58 and intrinsic critical current 24 μA are obtained in the using structure diameter 20 nmφ.
For the realization of high-performance spintronic devices, development novel magnetic materials/structures satisfying both large perpendicular anisotropy (PMA) and ultra-low Gilbert damping is strongly desired. Here, we show that insertion an ultrathin GdOx layer as a capping in double-barrier stacks provides such solution. The inserted prevents unintended intermixing among (CoFeB) oxide layers (MgO MgFeO), suppressing deterioration PMA damping. Remarkably, variation effective oxygen doping...
Abstract Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit that are particularly advantageous for the development of high-performance devices. Here, we report fully (001)-epitaxial growth a high-quality half-metallic NiMnSb half-Heusler alloy films their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices Ag spacer...
Voltage-driven magnetization switching is a promising solution for realizing ultralow-power magnetic memories with energy efficiency well beyond that of devices driven by electric current. For such applications, though, substantial reduction the write-error rate strongly needed. The authors show precision voltage-driven can be improved precise control voltage pulse's shape. Using proper fall time in write pulse effectively cancels drift, due to intrinsic damping, and helps reduce error. This...
Co2Fe0.4Mn0.6Si (CFMS) and Co2FeGa0.5Ge0.5 (CFGG) Heusler alloys are among the most promising thin film materials for spintronic devices due to a high spin polarization, low magnetic damping giant/tunneling magnetoresistance ratios. Despite numerous investigations of properties performed up now, magnetoelastic effects in these remain not fully understood; quite rare studies correlations between other properties, such as dissipation or anisotropy. In this research we have investigated...
Dynamic switching of magnetization driven by subnanosecond voltage pulses would be a central technology for realizing ultralow-power magnetic random-access memory. For practical applications, however, there is strong demand to reduce the write-error rate. This study shows that transitions between different precession orbits, as induced thermal fluctuations, play dominant role in probability write error. The can avoided choosing proper width pulse. These findings will promote development...
We develop perpendicularly magnetized magnetic tunnel junctions consisting of a recording layer exhibiting low damping to investigate the influence on write-error rate voltage-driven magnetization switching. The effective is reduced about one-third that conventional $\mathrm{Ta}$/$\mathrm{Co}\text{\ensuremath{-}}\mathrm{Fe}\text{\ensuremath{-}}\mathrm{B}$/$\mathrm{Mg}\mathrm{O}$ by eliminating spin pumping effect. contributes 3-orders-of-magnitude reduction in for longer write pulses, which...
Vertical spin valve devices with junctions of single- and bi-layer graphene interlayers sandwiched Fe20Ni80 (Permalloy) electrodes were fabricated by exploiting the direct growth on Permalloy. The linear current-voltage characteristics indicated that ohmic contacts realized at interfaces. systematic characterization revealed significant modification electronic state interfacial layer Permalloy surface, which indicates strong interactions interface. transport was attributable to...
We study the influence of inverse biases applied before and after a write pulse on write-error rate (WER) voltage-driven magnetization switching in magnetic tunnel junctions. It is demonstrated that bias effective not only for improving minimum value WER but also broadening operating pulse-width window. In contrast, an hardly improves or even narrows Numerical simulations based macrospin approximation reproduce these experimental results well detailed analysis trajectory reveals observed...
Abstract Perpendicular magnetic anisotropy (PMA) is becoming increasingly important in spintronics research, especially for high-density magnetoresistive random access memories (MRAMs). The PMA induced at an Fe/MgO interface widely used tunnel junctions. Here, we propose inserting ultrathin LiF layer the epitaxial junction. With a 0.3 nm-thick layer, large intrinsic energy, K i ,0 , of 2.8 mJ/m 2 was achieved. We also found that LiF/MgO bilayer tunneling barrier exhibited magnetoresistance...
The voltage-controlled magnetic anisotropy (VCMA) effect has been proposed as an energy efficient approach for controlling the direction of magnetization. To demonstrate scalability a magnetoresistive random access memory, we need to optimize perpendicular (PMA), tunnel magnetoresistance (TMR), and VCMA properties. Here, performed systematic investigation effects inserting post-oxidized MgAl layer on PMA, TMR, in epitaxial junctions (MTJs). PMA TMR have substantial dependences thickness...
Abstract We deposited an ultrathin CoFeB(1.1 nm) layer, which functions as a storage layer of MgO-based magnetic tunnel junctions for spin-transfer-torque (STT) magnetoresistive random-access memory (MRAM), on ϕ 300 mm wafers at 100 K and investigated its effect the magnetization dynamics CoFeB. observed clear reductions in both inhomogeneous linewidth total damping parameter CoFeB compared to those through improvement interfacial quality. The results show that deposition cryogenic...
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 CoFeB layers nanostructure, magnetic, and magneto-transport properties MTJs was investigated in detail. When deposited at 100 K, exhibited perpendicular anisotropy (PMA) 214 μJ/m2 voltage-controlled (VCMA) coefficient −45 fJ/V m, corresponding to 1.4- 1.7-fold enhancements PMA VCMA, respectively, compared...
One major cause of aquatic pollution is the accumulation heavy metal ions. This review aimed to examine application natural biofilm as biosorbent for Mg(II), Cr(VI), and Cu(II), an eco-friendly, economical, efficient remediation strategy. Biofilm matrices were collected from different freshwater ecosystems observe their biosorption properties. The compared EPM values biofilms showed a universal trend. Additionally, adsorption kinetics all three ions occurred within 1 minute. amount adsorbed...
We show spin-transfer-torque-driven vortex oscillations in current-perpendicular-to-plane giant magnetoresistance junctions using epitaxially grown ${\mathrm{Co}}_{2}{\mathrm{Fe}}_{x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Si}$ (CFMS) Heusler alloy thin films. The soft magnetic property and high spin polarization of CFMS enable us to realize oscillation emitting large microwave power with a low threshold current. output is maximized for certain Fe-Mn composition ratio associated reduction...
We study the dynamic switching properties of a nanomagnet under microwave electric field pumping. The periodic modulation an anisotropy induced by pumping efficiently excites uniform magnetization oscillation, allowing for precise control switching. Accurate shaping voltage waveform also enables us to investigate transient reaction relative phase difference signal. demonstrate both experimentally and theoretically existence dead angle in which oscillation is inhibited even though frequency...