A5055570618- Magnetic properties of thin films
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- ZnO doping and properties
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Magnetic Properties of Alloys
- Ferroelectric and Negative Capacitance Devices
- Advanced Memory and Neural Computing
- Semiconductor materials and devices
- Bone Tissue Engineering Materials
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Quantum and electron transport phenomena
- Rare-earth and actinide compounds
- Dental materials and restorations
- Magnetic Field Sensors Techniques
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Astro and Planetary Science
- Dental Implant Techniques and Outcomes
- Iron-based superconductors research
- Economic Theory and Policy
- Japanese History and Culture
- Metal and Thin Film Mechanics
Spintronics Research Network of Japan
2013-2024
Tohoku University
2014-2024
Japan Aerospace Exploration Agency
1992-2024
Kagoshima University Hospital
2024
Institute of Space and Astronautical Science
2023-2024
Yokohama National University
2024
Samsung (South Korea)
2021-2023
University of Alabama
2022
Akebono (Japan)
2021
Kōchi University
2021
We investigated perpendicular CoFeB-MgO magnetic tunnel junctions (MTJs) with a recording structure consisting of two interfaces, MgO/CoFeB (1.6 nm)/Ta (0.4 nm)/CoFeB (1.0 nm)/MgO. Thermal stability factor MTJ the having junction size 70 nmφ was increased by 1.9 from highest value MTJs single interface same device structure. On other hand, intrinsic critical current for spin transfer torque switching double- and single-interface comparable.
We investigate properties of perpendicular anisotropy magnetic tunnel junctions (MTJs) with a recording structure MgO/CoFeB/Ta/CoFeB/MgO down to junction diameter (D) 11 nm from 56 nm. Thermal stability factor (Δ) MTJ the starts decrease at D = 30 dependence Δ agrees well that expected blanket film taking into account change in demagnetizing factors MTJs. Intrinsic critical current (IC0) reduces entire investigated range. A ratio IC0 shows continuous increase
We study the device size dependence of spin-orbit torque induced magnetization switching in a Ta/CoFeB/MgO structure with perpendicular easy axis. The miniaturization from micrometer-sized wire to 80-nm dot results increase threshold current density Jth by one order, whereas increases only slightly further reducing down 30 nm. No significant is seen, as pulse width decreases 100 ms 3 ns. reveal that devices at reduced reasonably well explained macrospin model, which effects both...
Abstract Nanoscale magnetic tunnel junctions play a pivotal role in magnetoresistive random access memories. Successful implementation depends on simultaneous achievement of low switching current for the magnetization by spin transfer torque and high thermal stability, along with continuous reduction junction size. Perpendicular easy-axis CoFeB/MgO stacks possessing interfacial anisotropy have paved way down to 20-nm scale, below which new approach needs be explored. Here we show that...
Two types of tetragonal zirconia polycrystals (TZP), a ceria-stabilized TZP/Al2O3 nanocomposite (CZA) and conventional yttria-stabilized TZP (Y-TZP), were sandblasted with 70-μm alumina 125-μm SiC powders, then partially annealed at 500—1200°C for five minutes. Monoclinic ZrO2 content was determined by X-ray diffractometry Raman spectroscopy. Biaxial flexure test conducted on the specimens before after treatments. biaxial strength increased sandblasting, but decreased heat treatment....
Abstract The purpose of the present study was to evaluate mechanical durability a zirconia/alumina nanocomposite stabilized with cerium oxide (Ce‐TZP/Al 2 O 3 nanocomposite) in comparison yttria‐stabilized tetragonal zirconia polycrystals (Y‐TZP) and discuss its application on ceramic dental restorations. disk‐shaped specimens both materials were stored physiological saline solution at 80°C for 30 days, 4% acetic acid an autoclave 121°C 10 days. Before after storage, subjected biaxial...
Junction size dependence of critical current (IC0) for spin transfer torque switching and thermal stability factor (E/kBT) was examined in CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs). The IC0 increased with increasing recording layer area (Srec). On the other hand, E/kBT showed almost constant values even though Srec from ∼1500 nm2 (44 nmφ) to ∼5000 (76 nmφ). Both behavior can be explained assuming that nucleation type magnetization reversal takes place p-MTJs.
Junction size (D) dependence of thermal stability (Δ) factor and intrinsic critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C0</sub> ) were investigated for MgO/CoFeB/Ta/CoFeB/MgO recording structure in magnetic tunnel junctions (MTJs) having a CoFeB reference layer synthetic ferrimagnetic (SyF) layer. Δ the shows almost constant value down to 40 nm, whereas I linear on area, as similarly observed with single-interface....
We show that the magnetic characteristics of Ta|CoFeB|MgO heterostructures are strongly influenced by doping Ta underlayer with nitrogen. In particular, saturation magnetization drops upon underlayer, suggesting doped acts as a boron diffusion barrier. addition, thickness dead layer decreases increasing nitrogen doping. Surprisingly, interface anisotropy increases to ∼1.8 erg/cm2 when an optimum amount is introduced into underlayer. These results serves good for spintronic applications...
We show a three terminal magnetic tunnel junction (MTJ) with 10-nm thick channel based on an interconnection material Cu 10% Ir doping. By applying current density of less than 1012 A m−2 to the channel, depending direction, switching MTJ defined takes place. that spin transfer torque (STT) plays critical role in determining threshold current. assuming Hall effect being source STT, lower bound magnitude angle is evaluated be 0.03.
Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving chemically identifying each individual stacking layer remains challenging due to localized features that complicate characterizations limiting understanding of the physics MTJs. Here, we combine advanced electron microscopy, spectroscopy, first-principles calculations obtain direct structural chemical imaging atomically...
Magnetic heterostructures consisting of high-resistivity (238 ± 5 µΩ cm)-W/CoFeB/MgO are prepared by sputtering and their spin-orbit torques evaluated as a function W thickness through an extended harmonic measurement. dependence the torque with Slonczewski-like symmetry is well described drift-diffusion model efficiency parameter, so-called effective spin Hall angle, −0.62 0.03. In contrast, field-like one order magnitude smaller than shows no appreciable on thickness, suggesting different...
We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, which two successive voltage pulses are applied to utilize both spin-transfer torque electric field effect. Under this scheme, CoFeB/MgO junction with perpendicular easy axis is shown switch faster than by alone more reliably that fields alone.
Abstract The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based has spatial restrictions (few µm), whereas the long-range electrical using vortex STOs limited frequency responses in hundreds MHz (<500 MHz), restricting them on-chip GHz-range Here, we demonstrate four non-vortex uniformly-magnetized a single common current source both parallel series configurations at...
Abstract Making magnetic tunnel junctions (MTJs) smaller while meeting performance requirements is critical for future electronics with spin-transfer torque magnetoresistive random access memory (STT-MRAM). However, it challenging in the conventional MTJs using a thin CoFeB free layer capped an MgO because of increasing difficulties satisfying required data retention and switching speed at scales. Here we report single-nanometer consisting CoFeB/MgO multilayers, where number interfaces...
We study the spin-orbit torque induced magnetization switching in W/CoFeB/MgO heterostructures with W deposited under different sputtering conditions. show that crystal structure and resistivity of depend on employed Switching current nanoscale devices is smaller while effective anisotropy field larger for more resistive channel at lower power higher Ar gas pressure. The spin Hall angle evaluated from probability varies by a factor 2–3 depending controlled
Thermal stability factor Δ of the recording layer was studied in perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with various CoFeB thicknesses and junction sizes. In all series p-MTJs different thicknesses, is virtually independent sizes 48-81 nm diameter. The values increase linearly as thickness increases. slope linear fit explained well by a model based on nucleation-type magnetization reversal.
For the first time, we demonstrated 55 nmCMOS/ spin-orbit-torque-device hybrid magnetic randomaccess memory (SOT-MRAM) cell with field free writing. writing, developed canted SOT device under 300 mm BEOL process full compatible 400°C thermal tolerance. Moreover, its advanced as follows; channel layer PVD for high spin Hall angle tolerance, low damage RIE technology of MTJ TMR/thermal stability factor (Δ) and ultra-smooth surface metal via to reduce contact resistance. By above technologies,...
L 1 type Co-Pt ordered alloy films with a large uniaxial magnetic anisotropy, Ku, of the order 107erg∕cm3 were successfully fabricated at relatively low substrate temperatures 270–390°C using ultrahigh vacuum sputter film deposition. L11 films, ⟨111⟩ direction (easy axis magnetization) perpendicular to plane, on MgO(111) single crystal substrates and glass disks. The structure was formed in wide Pt content region 40–75at.%, Ku showed maximum around 50at.% content. values parameter S for...
We review recent developments in magnetic tunnel junctions with perpendicular easy axis (p-MTJs) for nonvolatile very large scale integrated circuits (VLSIs). So far, a number of material systems such as rare-earth/transition metal alloys, L1 0 -ordered ( Co, Fe )– Pt Co /( Pd, ) multilayers, and ferromagnetic-alloy/oxide stacks have been proposed electrodes p-MTJs. Among them, p-MTJs single or double stacks, particularly CoFeB–MgO , were shown to high potential satisfy major requirements...
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.
CoFeB/MgO heterostructures are a promising candidate for an integral component of spintronic devices due to their high magnetic anisotropy, low Gilbert damping, and excellent magnetoresistive properties. Here, we present experimental measurements atomistic simulations the temperature CoFeB thickness dependence spontaneous magnetization anisotropy in ultrathin films. We find that thermal fluctuations different between bulk interface magnetizations, interfacial originates from two-site...
Novel damage control integration process technology has been developed through development of new low-damage MgO deposition process, RIE and low temperature SiN-cap process. Application the to MTJ fabrication enabled us demonstrate an improvement TMR ratio, thermal stability factor, switching efficiency. Moreover, it is shown that endurance fabricated MTJs over 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> , although factor...