A5056430257- Magnetic properties of thin films
- ZnO doping and properties
- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Topological Materials and Phenomena
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Heusler alloys: electronic and magnetic properties
- GaN-based semiconductor devices and materials
- Electronic and Structural Properties of Oxides
- Magnetic Field Sensors Techniques
- Magneto-Optical Properties and Applications
- Chalcogenide Semiconductor Thin Films
- Physics of Superconductivity and Magnetism
- Silicon Carbide Semiconductor Technologies
- Advanced Condensed Matter Physics
- Graphene research and applications
- Advanced Memory and Neural Computing
- Ga2O3 and related materials
- Surface and Thin Film Phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Silicon and Solar Cell Technologies
- Magnetic Properties and Applications
- Electron and X-Ray Spectroscopy Techniques
Shanghai Institute for Science of Science
2025
Institute of Science Tokyo
2025
Tokyo Institute of Technology
2015-2024
Phenikaa University
2024
The University of Tokyo
2014-2023
Japan Science and Technology Agency
2005-2023
Spintronics Research Network of Japan
2016-2023
Ho Chi Minh City University of Technology
2021
Hanoi University
1997-2020
Kyoto Sangyo University
2020
Giant spin-orbit torque (SOT) from topological insulators (TIs) provides an energy efficient writing method for magnetic memory, which, however, is still premature practical applications due to the challenge of integration with tunnel junctions (MTJs). Here, we demonstrate a functional TI-MTJ device that could become core element future energy-efficient spintronic devices, such as SOT-based random-access memory (SOT-MRAM). The state-of-the-art tunneling magnetoresistance (TMR) ratio 102% and...
This review presents the recent progress in computational materials design, experimental realization, and control methods of spinodal nanodecomposition under three- two-dimensional crystal-growth conditions spintronic materials, such as magnetically doped semiconductors. The description nanodecomposition, performed by combining first-principles calculations with kinetic Monte Carlo simulations, is discussed together extensive electron microscopy, synchrotron radiation, scanning probe, ion...
Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well charge transport materials and devices. While metal-based spin-devices, such magnetic-field sensors magnetoresistive random access memory using giant magnetoresistance tunneling magnetoresistance, are already put practical use, semiconductor-based has greater potential for expansion because good compatibility with existing semiconductor technology. Many devices useful...
We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga1−x,Fex)Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy anomalous Hall effect measurements indicate intrinsic of these samples. The Curie temperature reaches 300 K 340 for x 25%, respectively, which are the highest values reported so far III-V semiconductors.
Spin-orbit torque (SOT) magnetization switching of ferromagnets with large perpendicular magnetic anisotropy has a great potential for the next-generation non-volatile magnetoresistive random-access memory (MRAM). It requires high-performance pure spin current source Hall angle and high electrical conductivity, which can be fabricated by mass production technique. In this work, we demonstrate ultrahigh efficient robust SOT in all-sputtered BiSb topological insulator - perpendicularly...
Electron effective mass (me*) in GaNxAs1−x/GaAs quantum wells (QWs) is investigated by the optically detected cyclotron resonance technique. The me* values of 0.12m0 and 0.19m0 are directly determined for 70-Å-thick QWs with N composition 1.2% 2.0%, respectively. This sizable increase electron consistent earlier theoretical predictions based on strong interaction lowest conduction band states upper lying or impurity induced incorporation N.
We show that by introducing isoelectronic iron (Fe) magnetic impurities and Beryllium (Be) double-donor atoms into InAs, it is possible to grow an n-type ferromagnetic semiconductor (FMS) with the ability control ferromagnetism both Fe independent carrier doping low-temperature molecular-beam epitaxy. demonstrate (In,Fe)As doped electrons behaves as electron-induced FMS. This achievement opens way realize spin-devices such spin light-emitting diodes or field-effect transistors, well helps...
We systematically investigate the crystal structure, magneto-optical properties, magnetization, and magnetotransport properties of a new ferromagnetic semiconductor $(\mathrm{G}{\mathrm{a}}_{1\ensuremath{-}x},\mathrm{F}{\mathrm{e}}_{x})\mathrm{Sb}$ grown by low-temperature molecular beam epitaxy. Crystal structure analyses x-ray diffraction, scanning transmission microscopy, electron diffraction indicate that thin films maintain zinc-blende up to $x=20%$. carried out characterizations...
The electron effective mass (m*) in n-type carrier-induced ferromagnetic semiconductor (In,Fe)As was estimated by using the thermoelectric Seebeck effect. It found that m* is 0.03 ∼ 0.17m0 depending on concentration, where m0 free mass. These values are similar to those of electrons conduction band n+ InAs. Fermi level EF located at least 0.15 eV above bottom. Our results indicate carriers reside band, rather than a hypothetical Fe-related itinerant impurity band.
Large spin splitting in the conduction band (CB) and valence (VB) of ferromagnetic semiconductors (FMSs), predicted by influential mean-field Zener model[1,2] assumed many spintronic device proposals[3-8], has never been observed mainstream p-type Mn-doped FMSs[9-15]. Here using tunnelling spectroscopy Esaki-diode structures, we report observation such a large spontaneous spin-splitting energy ({\Delta}E = 31.7 - 50 meV) CB bottom n-type FMS (In,Fe)As, which is surprising considering very...
Over the past two decades, intensive studies on various ferromagnetic semiconductor (FMS) materials have failed to realize reliable FMSs that a high Curie temperature (TC > 300 K), good compatibility with electronics, and characteristics superior those of their nonmagnetic host semiconductors. Here, we demonstrate new n-type Fe-doped narrow-gap III–V FMS, (In1−x,Fex)Sb. Its TC is unexpectedly high, reaching ∼335 K at modest Fe concentration (x) 16%. The anomalous Hall effect magnetic...
Abstract The large spin Hall effect in topological insulators (TIs) is very attractive for ultralow-power spintronic devices. However, evaluation of the angle and spin–orbit torque (SOT) TIs usually performed on high-quality single-crystalline TI thin films grown dedicated III-V semiconductor substrates. Here, we report room-temperature ultralow power SOT magnetization switching a ferrimagnetic layer by non-epitaxial BiSb deposited Si/SiO 2 We show that outperform heavy metals other...
The unidirectional spin Hall magnetoresistance (USMR) is one of the most complex spin-dependent transport phenomena in ferromagnet/nonmagnet bilayers, which involves injection and accumulation due to effect, scattering, magnon scattering at interface or bulk ferromagnet. While USMR metallic bilayers has been studied extensively very recent years, its magnitude (∼10−5) too small for practical applications. Here, we demonstrate a giant effect heterostructure BiSb topological insulator – GaMnAs...
The charge-to-spin conversion efficiency at the interface between a topological insulator and ferromagnetic (FM) layer can be enhanced by inserting an interlayer (ITL). However, mechanism of this enhancement is unclear. In work, we systematically investigate ITL effects introducing various metal, oxide, hybrid metal/oxide BiSb CoFe layer. Our findings revealed that using metallic NiFeGe or insulating MgO resulted in similarly high efficiencies, with highest achieved when employing NiFeGe/MgO...
Abstract In this study, we examine the impact of various seed layer materials that facilitate growth highly textured or epitaxial topological insulator Bi 0.9 Sb 0.1 (012) on Si/SiOx substrates. We found cubic-textured (100) tetragonal (001) layers undoped 1-x x with more square surface, while composed (111) polycrystalline or, alternatively, nanocrystalline amorphous are suitable for (012):X rectangular surface (012), where X is a dopant. By post annealing, obtained maximum spin Hall angle...
A systematic investigation of the effect rapid thermal annealing (RTA) on optical properties undoped GaNAs/GaAs structures is reported. Two effects are suggested to account for observed dramatic improvement in quality GaNxAs1−x/GaAs quantum after RTA: (i) improved composition uniformity GaNxAs1−x alloy, deduced from photoluminescence (PL), PL excitation and time-resolved measurements; (ii) significant reduction concentration competing nonradiative defects, revealed by optically detected...
An electron paramagnetic resonance (EPR) spectrum was observed at temperatures above 25 K in p-type 4H and 6H SiC irradiated with electrons. The center has ${\mathrm{C}}_{3\mathrm{V}}$ symmetry an spin $S=1/2.$ Using high frequency (\ensuremath{\sim}95 GHz) EPR it possible to obtain the detailed hyperfine structure due interaction four nearest silicon neighbors, identify defect as carbon vacancy positive-charge state $({\mathrm{V}}_{{\mathrm{C}}^{+}}).$ g values tensor of both polytypes are...
We report on the resonant tunneling effect and increase of magnetoresistance induced by it in ferromagnetic-semiconductor $\mathrm{GaMnAs}$ quantum-well (QW) heterostructures. The was observed when QW thickness from 3.8 to $20\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, which indicates that highly coherent occurs these quantum levels were successfully explained valence-band $k∙p$ model $p\text{\ensuremath{-}}d$ exchange interaction. It also found Fermi level electrode injecting carriers is...
A p-type ferromagnetic semiconductor (Ga1−x,Fex)Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray spectra indicate that (Ga,Fe)Sb layers have zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations band with spin-splitting induced s,p-d exchange...
We grew and characterized Bi1-xSbx thin films on GaAs(111)A substrates by molecular beam epitaxy. By optimizing the growth condition, we were able to grow epitaxially with Sb concentration ranging from 0% 100% epitaxial orientation of Bi1-xSbx(001)//GaAs(111). The conductivity exceeds 105 Ω−1 m−1 approaches those bulk values for thick enough films, which are higher than other Bi-based topological insulators at least an order magnitude. From temperature dependence their electrical...
We demonstrate electrical control of ferromagnetism in field-effect transistors with a trilayer quantum well (QW) channel containing an ultrathin n-type ferromagnetic semiconductor $(\mathrm{In},\mathrm{Fe})\mathrm{As}$ layer. A gate voltage is applied to the electron wave functions ${\ensuremath{\varphi}}_{i}$ QW, such that overlap and layer modified. The Curie temperature largely changed by 42%, whereas change sheet carrier concentration two three orders magnitude smaller than previous...
We report on the growth and characterization of BiSb thin films deposited sapphire substrates by sputtering deposition with Ar Kr plasma. By optimizing conditions, we are able to obtain quasi-single-crystal BiSb(001) equivalent twin crystals. The conductivity at studied thicknesses exceeds 105 Ω−1 m−1, reaching 1.8 × m−1 10 nm. From temperature dependence electrical resistivity, confirm existence metallic surface states. Our results demonstrate that it is possible sputtered quality...