A5042603137- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Magnetic Properties and Applications
- Advanced Memory and Neural Computing
- Semiconductor Quantum Structures and Devices
- Magnetic and transport properties of perovskites and related materials
- Quantum Information and Cryptography
- Characterization and Applications of Magnetic Nanoparticles
- Theoretical and Computational Physics
- Graphene research and applications
- Molecular Junctions and Nanostructures
- Multiferroics and related materials
- Magneto-Optical Properties and Applications
- Quantum optics and atomic interactions
- Surface and Thin Film Phenomena
- ZnO doping and properties
- 2D Materials and Applications
- Semiconductor materials and devices
- Metallic Glasses and Amorphous Alloys
- Atomic and Subatomic Physics Research
- Ferroelectric and Negative Capacitance Devices
- Advanced Condensed Matter Physics
- Advancements in Semiconductor Devices and Circuit Design
- Magnetic Field Sensors Techniques
National Institute of Advanced Industrial Science and Technology
2016-2025
Shinshu University
1994-2024
High Energy Accelerator Research Organization
2022
Tohoku University
2002-2021
Mitsui Mining & Smelting (Japan)
2019
NTT (Japan)
2019
Spintronics Research Network of Japan
2012-2016
Chiba University
2013-2014
NanoScale Corporation (United States)
2012
Nanosystem (Russia)
2012
Generation of practical random numbers (RNs) by a spintronics-based, scalable truly RN generator called "spin dice" was demonstrated. The utilizes the stochastic nature spin-torque switching in magnetic tunnel junction (MTJ) to generate RNs. We fabricated eight perpendicularly magnetized MTJs on single-board circuit and generated sequences RNs simultaneously. different were not correlated with each other, performing an exclusive OR (XOR) operation among them improved quality obtained nested...
We study the Kondo effect in a quantum dot coupled to ferromagnetic leads and analyze its properties as function of spin polarization leads. Based on scaling approach, we predict that for parallel alignment magnetizations strong-coupling limit is reached at finite value magnetic field. Using an equation motion technique, nonlinear transport through dot. For alignment, zero-bias anomaly may be split even absence external antiparallel symmetric coupling, peak only presence field, but shows...
We study theoretically the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in one- and two-dimensions presence of a Rashba spin-orbit (SO) coupling. show that rotation spin conduction electrons due to SO coupling causes twisted RKKY between localized spins which consists three different terms: Heisenberg, Dzyaloshinsky-Moriya, Ising interactions. also effective Hamiltonian reduces usual space where quantization axis one is rotated.
We fabricated a spin-torque oscillator (STO) having nanopillar-shaped magnetic tunnel junction with perpendicularly magnetized FeB free and in-plane CoFeB reference layers. The perpendicular magnetization of the was stabilized by strong anisotropy induced at both MgO barrier/FeB FeB/MgO cap interfaces. Under field (3 kOe), STO exhibited large emission power (0.55 µW), high frequency (6.3 GHz) Q factor (135) simultaneously, all which are largest to date among STOs. bias voltage dependence...
Copper nanoparticles (NPs) with an average particle diameter of 50-60 nm were successfully obtained by reducing aqueous solution a copper(II)-nitrilotriacetic acid complex hydrazine at room temperature under air atmosphere. NP-based nanopastes printed onto glass substrate using metal screen mask and pressureless sintered nitrogen atmosphere 200 °C for 30 min. The electrical resistivity the resulting copper electrode was 16 μΩ · cm. For metal-to-metal bonding test, nanopaste on oxygen-free...
We theoretically study the spin-dependent transport in a ferromagnet/superconductor/ferromagnet double tunnel junction. The tunneling current antiferromagnetic alignment of magnetizations gives rise to spin imbalance superconductor. resulting nonequilibrium density strongly suppresses superconductivity with increase bias voltage and destroys it at critical ${V}_{c}$. results provide new method not only for measuring polarization ferromagnets but also controlling magnetoresistance by applying voltage.
We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation, we observe initial phase Larmor precession whose coherence from light. To break electron-hole spin entanglement, utilized big discrepancy between transverse $g$ factors electrons and light-holes. The result encourages us make media converter flying photon qubits stationary electron-spin semiconductors.
We theoretically study the electron transport through a magnetic point contact (PC) with special attention given to effect of an atomic scale domain wall (DW). The spin precession conduction is forbidden in such DW and sequence quantized conductances depends on relative orientation magnetizations between left right electrodes. magnetoresistance strongly enhanced for narrow PC oscillates conductance.
The theory of electron correlation in semiconductor quantum dots is reviewed with emphasis on the physics strong magnetic fields. A brief survey dot fabrication and experimental results given, mechanics small numbers interacting electrons a discussed special values angular momentum number that ground state allowed to have, or magic numbers, are introduced. These selected because symmetry properties particularly evident limit field if system examined moving reference frame. Physically, this...
Microwave oscillation properties of spin torque vortex oscillators (STVOs) consisting an FeB free layer were investigated. Because a high MR ratio and large DC current, emission power up to 3.6 µW was attained in the STVO with thin 3 nm. In STOs thicker layer, e.g., 10 nm thick, we obtained Q factor greater than 6400 while maintaining integrated 1.4 µW. Such excellent microwave performance is breakthrough for mutual phase locking STVOs by electrical coupling.
This paper presents a review and future prospects for the tunnel magnetoresistance (TMR) effect in magnetic junction (MTJ) spin manipulation technologies such as spin-transfer torque (STT) magnetoresistive random access memory (MRAM). Major challenges ultrahigh-density STT-MRAM with perpendicular magnetization novel functional devices related to MRAM are discussed.
We investigated the Gilbert damping of thin films with a MgO-barrier/Fe80B20/MgO-cap/Ta structure, in which Fe80B20 layer corresponds to free perpendicularly magnetized magnetic tunnel junction, by using ferromagnetic resonance (FMR). systematically varied thickness MgO cap and estimated constant (α) measuring dependence FMR spectrum on field angle. The was found reduce α about 0.005, is less than half value without cap. significant reduction can be explained suppression spin pumping...
We investigated microwave oscillation in a sombrero-shaped nano-contact spin-torque oscillator under an external magnetic field with out-of-plane component. By increasing the field, we observed abrupt change from in-plane precession to around effective demagnetization of free layer. The optimized conditions yielded not only fundamental peak very large Q factor (3200) but also higher-order harmonic peaks frequencies up at least 45 GHz. A high and high-frequency oscillations are great...
Voltage-controlled magnetoresistive random access memory (VC-MRAM) is an emerging nonvolatile based on the voltage-controlled magnetic anisotropy (VCMA) effect. It has been garnering considerable attention because of its fast and low-power operation. However, two major issues must be addressed for practical applications. First, voltage-induced switching free layer magnetization sensitive to ultrashort voltage pulse duration. Second, write error rate (WER) high. To address these issues, a...
Abstract Short channel transistors are gaining attention for high-frequency applications. MoS 2 transistors, with their atomically thin structure, exhibit excellent on/off switching and low intrinsic capacitance. This study employs the nonequilibrium Green's function formalism to analyze electronic properties evaluate performance under a sub-10-nm metal gate using small-signal model. The findings reveal that can achieve cut-off frequencies in terahertz range, even presence of electron-phonon...
We have fabricated granular nanobridge structures consisting of electrodes separated by a nanometer-sized gap in which thin insulating CoAlO film is filled, and measured the current–bias voltage characteristics magnetic field to investigate spin-dependent transport. The Coulomb blockade with clear threshold (Vth) observed at 4.2 K. Tunnel magnetoresistance (TMR) enhanced fabricating nanobridges. TMR shows maximum exceeding about 30% slightly above Vth. This enhancement explained orthodox...
We study theoretically the spin-dependent transport in ferromagnet/normal-metal/ferromagnet double tunnel junctions by special attention to cotunneling Coulomb blockade region. The spin accumulation caused squeezes region when magnetizations ferromagnetic electrodes are antiparallel. Outside squeezed region, we propose a new anomalous where sequential tunneling one of bands is suppressed and that other not. In this magnetoresistance oscillates as function bias voltage. temperature...
We study the Kondo effect in electron transport through a quantum dot coupled to ferromagnetic leads, using real-time diagrammatic technique which provides systematic description of nonequilibrium dynamics system with strong local correlations. evaluate theory an extension `resonant tunneling approximation', introduced earlier, by introducing self-energy off-diagonal component reduced propagator spin space. In this way we develop charge and conserving approximation that accounts not only for...