A5078253582- Iron oxide chemistry and applications
- Magnetic Properties and Synthesis of Ferrites
- Multiferroics and related materials
- Magnetic properties of thin films
- Magneto-Optical Properties and Applications
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Metamaterials and Metasurfaces Applications
- Organic and Molecular Conductors Research
- Advanced Battery Materials and Technologies
- Phase Change Materials Research
- Thermal Expansion and Ionic Conductivity
- Perovskite Materials and Applications
- Magnetism in coordination complexes
- Transition Metal Oxide Nanomaterials
- Characterization and Applications of Magnetic Nanoparticles
- Advanced Antenna and Metasurface Technologies
- Terahertz technology and applications
- Ferroelectric and Piezoelectric Materials
- Photonic Crystals and Applications
- Porphyrin and Phthalocyanine Chemistry
- Clay minerals and soil interactions
- Ga2O3 and related materials
- Advanced Photocatalysis Techniques
- Nanoparticle-Based Drug Delivery
The University of Tokyo
2016-2025
Bunkyo University
2021
Chiba University
2014
Magnetic ferrites such as Fe3O4 and Fe2O3 are extensively used in a range of applications because they inexpensive chemically stable. Here we show that rhodium-substituted ε-Fe2O3, ε-RhxFe2−xO3 nanomagnets prepared by nanoscale chemical synthesis using mesoporous silica template, exhibit huge coercive field (Hc) 27 kOe at room temperature. Furthermore, crystallographically oriented sample recorded an Hc value 31 kOe, which is the largest among metal-oxide-based magnets comparable to those...
Abstract Iron(III) oxide shows a polymorphism, characteristic of existence phases with the same chemical composition but distinct crystal structures and, hence, physical properties. Four crystalline iron(III) have previously been identified: α-Fe 2 O 3 (hematite), β-Fe , γ-Fe (maghemite) and ε-Fe . All four easily undergo various phase transformations in response to heating or pressure treatment, usually forming hexagonal which is most thermodynamically stable Fe polymorph under ambient...
Abstract Development of nanometer-sized magnetic particles exhibiting a large coercive field ( H c ) is in high demand for densification recording. Herein, we report single-nanosize (i.e., less than ten nanometers across) hard ferrite. This ferrite composed ε-Fe 2 O 3 , with sufficiently value recording systems and remarkably anisotropy constant 7.7 × 10 6 erg cm −3 . For example, 8.2-nm nanoparticles have an 5.2 kOe at room temperature. A colloidal solution these possesses light orange...
Abstract Commonly available heat-storage materials cannot usually store the energy for a prolonged period. If solid material could conserve accumulated thermal energy, then its application potential is considerably widened. Here we report phase transition that can latent heat in wide temperature range, T <530 K and release on of pressure. This stripe-type lambda-trititanium pentoxide, λ-Ti 3 O 5 , which exhibits solid–solid to beta-trititanium β-Ti . The pressure conversion extremely...
Abstract Epsilon iron oxide (ε-Fe2O3) is attracting global attention as a magnetic material with large anisotropy. In this article, the optical properties of ε-Fe2O3 nanoparticles and metal-substituted series ε-MxFe2−xO3 (M = Ga, In, Al) are studied over wide frequency range from millimeter-wave to terahertz-wave region, 30 GHz–30 THz, using terahertz time-domain, far-infrared, Raman spectroscopies. To understand spectroscopic data, first-principles calculations electronic structure phonon...
Light- or electromagnetic wave-responsive magnetism is an attractive issue in spin chemistry and optical materials science. Herein we show the magnetization reversal induced by visible-light pulsed laser ultrafast dynamic magnetooptical effect caused terahertz (THz) irradiation onto chemically synthesized magnetic films based on gallium–titanium–cobalt-substituted ε-Fe2O3 (GTC-ε-Fe2O3) nanoparticles. Visible-light switches sign of Faraday GTC-ε-Fe2O3 films. On other hand, irradiating film...
In the era of Big Data and Internet Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term storage. To archive an enormous amount data, further increase recording density necessary. Herein new methodology, "focused-millimeter-wave-assisted (F-MIMR)," proposed. test films based on epsilon iron oxide nanoparticles prepared focused-millimeter-wave generator constructed using terahertz (THz) light. Irradiating...
ε-Fe2O3 is known to exhibit a large coercive field of 20 kOe at room temperature. In this work, we examine the electronic structure and magnetic properties using first-principles calculation discrete variational (DV)-Xα molecular orbital calculation. The shows that charge-transfer type insulator with valence band O2p conduction Fe3d. optical transition an indirect from Γ S point. density states (DOS) four nonequivalent Fe sites (FeA, FeB, FeC, FeD) indicates has ferrimagnetic ordering due α...
Magnetic ferrites are stable, sustainable, and economical. Consequently, they have been used in various fields. The development of large coercive field (large Hc) magnetic is a very important but challenging issue to accelerate the spread use expand practical applications. In this study, we prepared rhodium-substituted ε-iron oxide film observed remarkably Hc value 35 kOe at room temperature. This largest among date. Such large-Hc ferrite expected greatly application ferrites. Furthermore,...
Biocompatibility restrictions have limited the use of magnetic nanoparticles for hyperthermia therapy to iron oxides, namely magnetite (Fe3O4) and maghemite (γ-Fe2O3). However, there is yet another oxide phase that has not been considered so far, in spite its unique properties: ε-Fe2O3. Indeed, whereas Fe3O4 γ-Fe2O3 a relatively low coercivity, ε-Fe2O3 exhibits giant coercivity. In this report, heating power comparison with similar size (∼20 nm) was measured wide range field frequencies...
Solid refrigerants exhibiting a caloric effect upon applying external stimuli are receiving attention as one of the next-generation refrigeration technologies. Herein, we report new inorganic refrigerant, rubidium cyano-bridged manganese-iron-cobalt ternary metal assembly (cyano-RbMnFeCo). Cyano-RbMnFeCo shows reversible barocaloric with large adiabatic temperature changes 74 K (from 57 °C to -17 °C) at 340 MPa, and 85 88 3 560 MPa. Such have yet be reported among effects in solid-solid...
Terahertz waves are gathering attention as carrier for next-generation wireless communications such sixth-generation communication networks and autonomous driving systems. Electromagnetic-wave absorbers the terahertz-wave region necessary to ensure information security avoid interference issues. Herein we report a high-performance absorber composed of composite metallic λ-Ti3O5 insulating TiO2 nanocrystals (λ-Ti3O5@TiO2). This material exhibits strong absorption with high values real...
The phase transition between gamma-trititanium-pentoxide (γ-Ti3O5) and delta-trititanium-pentoxide (δ-Ti3O5) was clarified from both experimental theoretical viewpoints. With decreasing temperature, the monoclinic I2/c crystal structure of γ-Ti3O5 found to switch a P2/a δ-Ti3O5 due lowering symmetry. Electrical conductivity (σ) measurement shows that behaves like metallic conductor with σ value 4.7 S cm–1 at 320 K, while semiconductive property 2.5 × 10–5 70 K. Optical also supports is...
In this work, we prepared indium-substituted ε-iron oxide (ε-InxFe2−xO3) spherical nanoparticles by a combination method of reverse-micelle and sol-gel techniques. The powder X-ray diffraction pattern with Rietveld analysis shows that ε-InxFe2−xO3 has an orthorhombic crystal structure (space group: Pna21), the In3+ ions mainly replace Fe3+ at B site among four nonequivalent sites (A–D sites). magnetic measurements show coercive field (Hc) 300 K decreases increasing x, i.e., Hc = 21.9 kOe (x...
Abstract From the viewpoints of large capacity, long‐term guarantee, and low cost, interest in magnetic recording tapes has undergone a revival as an archive storage media for big data. Herein, we prepared new series metal‐substituted ϵ‐Fe 2 O 3 , ϵ‐Ga III 0.31 Ti IV 0.05 Co II Fe 1.59 nanoparticles with average size 18 nm. Ga, Ti, cations tune properties to specifications demanded tape. The coercive field was tuned 2.7 kOe by introduction single‐ion anisotropy on ( S =3/2) along c‐axis....
Abstract Ferrite magnets have a long history. They are used in motors, magnetic fluids, drug delivery systems, etc. Herein we report mesoscopic ferrite bar magnet based on rod-shaped ε-Fe 2 O 3 with large coercive field (>25 kOe). The –based is single crystal domain along the longitudinal direction. A wide frequency range spectroscopic study shows that crystallographic -axis of , which corresponds to direction magnet, plays an important role linear and non-linear magneto-optical...
Recent developments in terahertz technologies provide new tools for analysis, inspection, and nondestructive sensing. If a heavy atom is encapsulated cage of porous material, the should vibrate slowly resonate with low-frequency light. From this perspective, cyanide-bridged metal framework suitable system because it contains many cages that can adsorb Cs ions. Herein we show vibration mode ion framework. First-principles phonon calculations time-domain spectroscopy (THz-TDS) measurements...
Abstract The accumulated heat energy of a heat-storage material is typically released over time. If could preserve its for prolonged period, the applicability such materials would be expanded greatly. Herein we report newly fabricated that can store latent long period and release upon demand by applying an extremely low pressure. This block-type lambda trititanium pentoxide (block-type λ-Ti 3 O 5 ). λ-phase accumulates large 237 kJ L −1 exhibits pressure-induced phase transition to beta...
Extremely low-frequency optical phonon mode in Rb-intercalated two-dimensional cyanide-bridged Co–W bimetal assembly and its temperature- photo-induced switching effect.
Abstract We study by femtosecond optical pump‐probe spectroscopy the photoinduced charge transfer (CT) in RbMnFe Prussian blue analogue. Previous studies evidenced local nature of Mn III Fe II → process, occurring within less than 1 ps. Here we show experimentally that two photoswitching pathways exist, depending on excitation pump wavelength, which is confirmed band structure calculations. Photoexcitation α spins corresponds to Mn(d‐d) band, drives reverse Jahn–Teller distortion through...
In this study, we demonstrate a synthesis of rhodium substituted ε-iron oxide, ε-RhxFe2−xO3 (0 ≤ x 0.19), nanoparticles in silica. The features sol–gel method to coat the metal hydroxide sol containing Fe3+ and Rh3+ ions with silica via hydrolysis alkoxysilane form composite gel. obtained samples are barrel-shaped average long- short-axial lengths approximately 30 nm 20 nm, respectively. crystallographic structure study using X-ray diffraction shows that has an orthorhombic crystal Pna21...
Abstract Phase transition materials are attractive from the viewpoints of basic science as well practical applications. For example, optical phase used for recording media. If a in condensed matter could be predicted or designed prior to synthesizing, development will accelerated. Herein we show logical strategy designing accompanying thermal hysteresis loop. Combining first-principles phonon mode calculations and statistical thermodynamic considering cooperative interaction predicts...