A5052627336- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Superconductivity in MgB2 and Alloys
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Corporate Taxation and Avoidance
- Magnetic and transport properties of perovskites and related materials
- Intellectual Capital and Performance Analysis
- Inorganic Chemistry and Materials
- Boron and Carbon Nanomaterials Research
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Inorganic Fluorides and Related Compounds
- Multiferroics and related materials
- Superconducting Materials and Applications
- Magnetic Properties and Synthesis of Ferrites
- Topological Materials and Phenomena
- Copper Interconnects and Reliability
- MXene and MAX Phase Materials
- Magnetic Properties of Alloys
- Magneto-Optical Properties and Applications
- High-pressure geophysics and materials
- Crystal Structures and Properties
- Semiconductor materials and interfaces
- Microwave Dielectric Ceramics Synthesis
National Institute of Advanced Industrial Science and Technology
2014-2023
Kurume Institute of Technology
2022
Hiroshima University
2022
Suzuki (Japan)
2009-2013
Osaka University
2007
Tokyo University of Science
2006
Japan Science and Technology Agency
2001-2005
Aoyama Gakuin University
1989-1995
We have synthesized a series of oxygen-deficient, fluorine-free polycrystalline samples with nominal chemical formula NdFeAsO 1- y using high-pressure technique. The ZrCuSiAs type crystal structure, as expected for NdFeAsO, is formed the main phase composition 0≤ ≤0.6. Sharp superconducting (SC) transition their temperature ( T c ) high 54 K observed 0.3≤ ≤0.8 samples, which higher than that F-doped NdFeAsO. While does not depend on , SC volume fraction shows maximum at = 0.4. Around same...
High-density bulk materials of a recently discovered 40 K intermetallic MgB2 superconductor were prepared by high-pressure sintering. Superconducting transition with the onset temperature 39 was confirmed both magnetic and resistive measurements. Magnetization versus field (M–H) curve shows behavior typical type-II lower critical Hc1(0) estimated from M–H is 0.032 T. The sample good connection between grains current density Jc magnetization hysteresis using size 5×104 A/cm2 at 20 1 Upper...
In-plane microwave penetration depth lambda_{ab} and quasiparticle conductivity at 28 GHz are measured in underdoped single crystals of the Fe-based superconductor PrFeAsO_{1-y} (T_{c} approximately 35 K) by using a sensitive superconducting cavity resonator. lambda_{ab}(T) shows flat dependence low temperatures, which is incompatible with presence nodes gap Delta(k). The temperature superfluid density demonstrates that nonzero (Delta/k_{B}T_{c} greater, similar1.6) all over Fermi surface....
We study the new binary intermetallic superconductor MgB(2) using high-resolution photoemission spectroscopy. The superconducting-state spectrum measured at 5.4 K shows a coherent peak with shoulder structure, in sharp contrast to that expected from simple isotropic-gap opening. can be well reproduced weighted sum of two Dynes functions gap sizes 1.7 and 5.6 meV. Temperature-dependent both gaps close bulk transition temperature. These results provide spectroscopic evidence for multiple MgB(2).
We investigated the optical spectrum of Ba(Fe1-xCox)2As2 single crystals with various doping levels. It is found that low-energy conductivity this system can be decomposed into two components: a sharp Drude term and broad "incoherent" term. For compounds showing magnetic order, gap appears predominantly in component, while an s-wave like superconducting opens both components for highly doped compounds. The weight steadily increases as proceeds, consistent electron system. On other hand,...
The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. results show that superconducting gaps with values 5.5 and 2.2 meV open on the sigma band pi band, respectively, but both close at bulk transition temperature, providing a definitive experimental evidence for two-band superconductivity strong interband pairing interaction in MgB2. experiments validate role k-dependent electron-phonon coupling as origin multiple-gap well high temperature
We report unusual magnetic and superconducting (SC) characteristics in multilayered ${\mathrm{CuO}}_{2}$ planes Hg- Cu-based high-${T}_{c}$ cuprates through the ${}^{63}\mathrm{Cu}\ensuremath{-}\mathrm{NMR}$ measurements. These compounds, which number of (n) ranges from 3 to 5 a unit cell, include crystallographically inequivalent outer (OP) inner (IP) plane that are surrounded by pyramidal square oxygen, respectively. The Knight shift ${(}^{63}K)$ at OP IP exhibits respective characteristic...
We report a site selective Cu-NMR study on underdoped Hg-based five-layered high-Tc cuprate HgBa2Ca4CU5O(12+delta) with Tc = 72 K. Antiferromagnetism (AFM) has been found to take place at T(N) 290 K, exhibiting large antiferromagnetic moment of 0.67-0.69 microB three inner planes (IP). This value is comparable the values reported for nondoped cuprates, suggesting that IP may be in nearly regime. Most surprisingly, AFM order also detected M(AFM)(OP) 0.1 even two outer (OP) are responsible...
Local magnetic measurements are used to quantitatively characterize heterogeneity and flux line pinning in ${\text{PrFeAsO}}_{1\ensuremath{-}y}$ NdFeAs(O,F) superconducting single crystals. In spite of spatial fluctuations the critical current density on macroscopic scale, it is shown that major contribution comes from collective vortex lines by microscopic defects mean-free-path fluctuation mechanism. The defect extracted experiment corresponds dopant atom density, which means atoms play an...
We report the 75 As nuclear magnetic resonance (NMR) measurement of hole-doped superconductor Ba 1- x K Fe 2 with different lattice parameters and superconducting volume fractions ( T c ≃38 K). As-NMR spectra revealed that magnetically ordered phases are microscopically separated. The spin-lattice relaxation rate 1/ 1 in normal state reflects existence a large two-dimensional antiferromagnetic spin fluctuation. down to lowest temperature varies close 3 . In addition, it exhibits no coherence...
The transport properties of dense polycrystalline and single-crystalline ${\mathrm{MgB}}_{2}$ platelets have been measured to determine the effects grain size on upper critical field ${H}_{c2}$ anisotropy parameter. in is enhanced magnetic-field-induced broadening significantly reduced with increasing size, probably due contamination at boundaries. Single-crystalline exhibits remarkable ${H}_{c2}(T)$ irreversibility ${H}^{*}(T)$...
We have studied the lower critical fields ${H}_{c1}$ of superconducting iron oxipnictide ${\text{PrFeAsO}}_{1\ensuremath{-}y}$ single crystals for $\mathbit{H}$ parallel and perpendicular to $ab$ planes. Measurements local magnetic induction at positions straddling sample edge by using a miniature Hall-sensor array clearly resolve first flux penetration from Meissner state. The temperature dependence $\mathbit{H}\ensuremath{\parallel}c$ is well scaled in-plane depth without showing any...
We report the fabrication of small (Ba,A)Fe2As2 (A: Na, K) coils using 10 m-class long round wires, fabricated by powder-in-tube (PIT) method. Coils are sintered hot-isostatic-press (HIP) technique after glass-fiber insulations installed. Critical current (Ic) whole coil (Ba,Na)Fe2As2 and (Ba,K)Fe2As2 60 A 66 under self-field, generated magnetic fields at center reach 2.6 kOe 2.5 kOe, respectively. Furthermore, largest transport critical density (Jc) Ic in wires picked up from 54 kAcm-2 51.8...
We report the frequency and temperature dependence of dielectric constant polycrystalline ErFe 2 O 4-δ with different degrees oxygen deficiency δ. A large relaxation, order magnitude 10 4 nearly Debye type, is observed in magnetically ordered states within ranges 150 K to 290 1 kHz 3 MHz, respectively. The dispersion larger sample more deficiency. From characteristic frequency, we conclude that elementary process related electron hopping between Fe 2+ 3+ ions. value consistent existence...
We performed the dc resistivity and ZF 75As-NMR measurement of BaFe2As2 under high pressure. The T-P phase diagram determined from anomalies clearly revealed that SDW anomaly is quite robust against P.
We fabricated (Ba,Na)Fe2As2 superconducting wires using the powder-in-tube method and hot isostatic pressing. By improving powder synthesis processes compared with previous studies, highly pure raw materials for wire fabrication were obtained. The largest transport critical current density (Jc) reached 40 kAcm-2 at T = 4.2 K under a magnetic field of 100 kOe. This value exceeds not only Jc but also those all iron-based round wires. Improvements polycrystalline play key role enhancement Jc....
We report the iron (Fe) isotope effect on transition temperature (Tc) in oxygen-deficient SmFeAsO_{1-y}, a 50 K-class Fe-based superconductor. For optimally-doped samples with Tc = 54 K, change of Fe average atomic mass (MFe) causes negligibly small shift Tc, coefficient (alphaFe) as -0.024 \pm 0.015. This result contrasts finite, inverse observed (Ba,K)Fe2As2, indicating that contribution electron-phonon interaction markedly differs between these two high-Tc superconductors.
We have characterized the ground state of Sr3Ir2O7 by performing measurements electrical resistivity, magnetic susceptibility, magnetization, specific heat and electron diffraction (ED). Polycrystalline samples been synthesized using a high-pressure technique. exhibits weak ferromagnetism with small ferromagnetic component (2 × 10−3 μB/Ir) below TC∼280 K. The temperature dependence resistivity ρ shows semiconducting-like behaviour; dρ/dT<0 an anomaly near TC. From result for heat, λ-type...
We succeeded in synthesizing a new intermetallic compound with AuCu3-type structure, LaBi3, by utilizing high-pressure technique. Reacting Bi and LaBi at 450 °C under pressure of 3.4 GPa resulted the crystallization LaBi3 an a-axis lattice parameter Sharp superconducting transitions were observed both its magnetic susceptibility electrical resistivity 7.3–7.4 K. The upper critical field Ginzburg–Landau coherence length ξ0 estimated to be 1.70 T 139 Å, respectively. transition temperature Tc...
Dielectric dispersion was observed in a single crystal with the composition of ErFe 2 O 3.95 below magnetic transition temperature. It is characterized by large dielectric constant order 10 4 , and Debye-type frequency dependence like polycrystalline samples same substance which we reported previous paper. Large anisotropy exists strength ε s - ∞ characteristic relaxation dispersion. The higher within c -plane than along -axis, while much larger -axis -plane. sample cannot be explained...