A5086621181- Magnetic properties of thin films
- Magnetic Properties and Applications
- Quantum and electron transport phenomena
- Magneto-Optical Properties and Applications
- Physics of Superconductivity and Magnetism
- ZnO doping and properties
- Advanced Memory and Neural Computing
- Magnetic Properties of Alloys
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Field Sensors Techniques
- Neural Networks and Applications
- Metallic Glasses and Amorphous Alloys
- Ferroelectric and Negative Capacitance Devices
- Force Microscopy Techniques and Applications
- Advanced Condensed Matter Physics
- Magnetic Properties and Synthesis of Ferrites
- Microwave and Dielectric Measurement Techniques
- Multiferroics and related materials
- Electric Motor Design and Analysis
- Mechanical and Optical Resonators
- Magnesium Alloys: Properties and Applications
- Photonic Crystals and Applications
- Advanced Data Storage Technologies
National Institute of Advanced Industrial Science and Technology
2016-2025
Toshiba (Japan)
2024
National Institute for Materials Science
2024
North Carolina State University
2017
Spintronics Research Network of Japan
2016
Carnegie Mellon University
2001-2013
Okayama University
2011
Voltage control of magnetic anisotropy (VCMA) in an ultrathin ferromagnet metal layer is a promising approach for ultralow-power spin manipulation, but interface effects spoil its efficiency applications such as memory devices. The authors study VCMA the fully epitaxial Fe tunnel junction, and achieve almost 300 fJ V${}^{-1}$ m${}^{-1}$ with high perpendicular anisotropy, which satisfies requirements gigabit-class spintronic memory.
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...
Voltage control of spin enables both a zero standby power and ultralow active consumption in spintronic devices, such as magnetoresistive random-access memory devices. A practical approach to achieve voltage is the electrical modulation spin–orbit interaction at interface between 3d-transition-ferromagnetic-metal dielectric layers magnetic tunnel junction (MTJ). However, we need initiate new guideline for materials design improve voltage-controlled anisotropy (VCMA) perpendicular (PMA). Here...
Abstract We investigated the write error rate (WER) for voltage-driven dynamic switching in magnetic tunnel junctions with perpendicular magnetization. observed a clear oscillatory behavior of probability respect to duration pulse voltage, which reveals precessional motion magnetization during voltage application. experimentally demonstrated WER as low 4 × 10 −3 at corresponding half precession period (∼1 ns). The comparison between results experiment and simulation based on macrospin model...
The perpendicular magnetic anisotropy of an Ir/CoFeB/MgO trilayer was investigated after annealing at temperatures ranging from 200 to 350 °C. In the system annealed 300 °C, we measured interface energy 1.9 mJ/m2. Further led mixing buffer and ferromagnet, degrading properties latter. addition, show dependence on bias voltage. presented is important for development tunnel junctions storage applications.
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.
In this study, we demonstrate voltage-driven dynamic magnetization switching for the write error rate (WER) of order 10−5. The largest voltage effect on perpendicular magnetic anisotropy in Ta/(CoxFe100–x)80B20/MgO structure (x = 0, 10, 31, 51) is obtained x 31 after annealing at 250 °C. Based investigations using perpendicularly magnetized tunnel junctions that have different (Co31Fe69)80B20 free layer thicknesses, improvement thermal stability factor important to reduce WER. Our results...
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.
We investigated the effect of voltage on perpendicular magnetic anisotropy in an ultrathin Fe80B20 layer sandwiched between two MgO barrier layers with different thicknesses, which bias is predominantly applied to one layers. The application both positive and negative voltages enhanced anisotropy, contrast odd function dependence previously observed a MgO/ferromagnetic metal/non-magnetic metal structure. Moreover, for voltages, large change slope 108 fJ/Vm was demonstrated. These results...
Spin torque oscillator (STO) has been attracting a great deal of attention as candidate for the next generation microwave signal sources various modern electronics systems since its advent. However, phase noise STOs under free running oscillation is still too large to be used in practical applications, thus an industrially viable means stabilize strongly sought. Here we demonstrate implementation locked loop using STO voltage controlled (VCO) that generates 7.344 GHz stabilized by 153 MHz...
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...
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...
We present a measurement technique for performing spatially resolved ferromagnetic resonance and directly imaging quantized magnetostatic modes in magnetic samples that undergo high frequency drive fields (up to 8 GHz). The dynamic response of 50×50 μm2 permalloy structure (100 nm thick) under 7.04 GHz highly nonuniform field was measured as function the dc bias using this technique. magnetization variation observed indicates mode waves appear at certain fields, with number nodes decreasing...
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...
The oscillation properties of a spin torque oscillator consisting perpendicularly magnetized free layer and an in-plane pinned are studied based on analysis the energy balance between damping. critical value external magnetic field applied normal to film plane is found, below which controllable range frequency by current suppressed. depends anisotropy, saturation magnetization, parameter.
We systematically investigated the Gilbert damping (α) and interfacial perpendicular magnetic anisotropy (Ki) in tunnel junctions with a MgO-barrier/FeB/MgO-cap layered structure using spin-torque diode effect. By increasing MgO cap thickness, α decreased, whereas Ki increased monotonically. Values down to 0.0054 for up 3.3 erg/cm2 were obtained thickness of 0.6 nm. The small large suggest that MgO-capped FeB is suitable free layer spintronics devices such as oscillators random access memories.
Magnetization switching assisted by high-frequency voltage was demonstrated in magnetic tunnel junctions with perpendicular magnetization. Ferromagnetic resonance excited instead of a field. A frequency-dependent reduction the field (coercive force) clearly observed maximum rate more than 80% under radio-frequency power application 3 dBm. The developed technique can provide novel approach to energy-assisted magnetization low ohmic dissipation.
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 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...
This work presents experimental results of magnetostatic mode excitation using scanning Kerr microscopy under continuous sinusoidal in the microwave frequency range. technique was applied to $100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick permalloy coupons excited two different ways. In first experiment, uniform (Kittel) at frequencies $2.24--8.00\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$. The resonant condition effectively described with conventional Kittel equation. LLG damping parameter...