共查询到20条相似文献,搜索用时 15 毫秒
1.
First principles of FLAPW-GGA calculations have been performed with the purpose to understand the peculiarities of band structure
and Fermi surface topology for recently discovered 37 K superconductor: Sr4V2Fe2As2O6—in comparison with isostructural phase Sr4Sc2Fe2As2O6. Our main finding is that the replacement of Sc with V leads to drastic transformation of electronic, magnetic and conductive
properties of these materials: as against non-magnetic Sr4Sc2Fe2As2O6 which is formed from non-magnetic conducting [Fe2As2] and insulating [Sr4Sc2O6] blocks, Sr4V2Fe2As2O6 consists of non-magnetic conducting [Fe2As2] blocks and [Sr4V2O6] blocks which exhibit magnetic half-metallic properties. 相似文献
2.
Yun-Lei Sun Abduweli Ablimit Jin-Ke Bao Hao Jiang Jie Zhou Guang-Han Cao 《Science and Technology of Advanced Materials》2013,14(5)
AbstractSingle crystals of a new iron-based superconductor Ba2Ti2Fe2As4O have been grown successfully via a Ba2As3-flux method in a sealed evacuated quartz tube. Bulk superconductivity with Tc ~ 21.5 K was demonstrated in resistivity and magnetic susceptibility measurements after the as-grown crystals were annealed at 500 °C in vacuum for a week. X-ray diffraction patterns confirm that the annealed and the as-grown crystals possess the identical crystallographic structure of Ba2Ti2Fe2As4O. Energy-dispersive x-ray spectra indicate that partial Ti/Fe substitution exists in the [Fe2As2] layers and the annealing process redistributes the Ti within the Fe-plane. The ordered Fe-plane stabilized by annealing exhibits superconductivity with magnetic vortex pinned by Ti. 相似文献
3.
Z. L. Liu Y. J. Liu K. L. Yao Z. H. Ding J. Tao X. Wang 《Journal of Materials Synthesis and Processing》2002,10(2):83-87
Magnetic Fe3O4 nanoparticles with size below 10 nm have been prepared by the aqueous phase coprecipitation method. The Fe3O4 nanoparticles show typical superparamagnetism. Comparison is made between the dispersed sample and the powder sample, and the results are discussed. 相似文献
4.
The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 spheres have been prepared by an in situ reaction using different molar ratios of Fe3+/Fe2+ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO2 as core and Fe3O4 nanoparticles as shell depend on the molar ratio of Fe3+/Fe2+. 相似文献
5.
NH4Zr2V3O12, a new proton conductor, has been synthesized by flux, melt and hydrothermal methods. The crystals were subjected to X-ray
diffraction, differential thermal analysis, infrared spectroscopy and impedance measurements. 相似文献
6.
A new piezoelectric single crystal, Sr3Ga2Ge4O14 (SGG), has been grown successfully by the vertical Bridgman method with crucible-sealing technique. SGG crystal up to 2″
in diameter has been obtained. The relative dielectric constants, the piezoelectric strain constants, elastic compliance constants
and electromechanical coupling factors have been determined with resonance and anti-resonance frequencies method by using
the impedance analyzer (Agilent 4294A). The results show that the piezoelectric strain constants and electromechanical coupling
factors of SGG single crystal are higher than those of LGS single crystals making it a potential substrate material for surface-acoustic
wave applications. 相似文献
7.
Measurements of the entropy change are reported for the high-temperature metal-insulator (MI) transitions in the (V1–xCrx)2O3 and (V1–xAlx)2O3 systems. It is emphasized that the entropy of the I phase exceeds that of the M phase. Evidence is presented to show that the M and I phases coexist over a narrow temperature range. The transformation is attended by enormous hysteresis effects; these indicate that the lattice plays an important role in the transition. The probable role of Cr3+ and Al3+ as a dopant in the V2O3 lattice is briefly discussed. A phase diagram for the dilute V2O3-Al2O3 alloy system is presented. 相似文献
8.
A special neutron scattering technique has been used to discover an incommensurate fluctuation in Bi2Sr2CaCu2O8 that appears below Tc. The fluctuation is identified as a dynamic charge density wave since its scattering intensity appears to increase with increasing
momentum transfer. The fluctuation is found at a wavevector near 2kF and could be associated with a dynamic stripe phase. 相似文献
9.
Two representative superconductors, UPt3 and Sr2RuO4, are comparatively studied on the basis of a general symmetry argument. The existing experimental data set for both systems strongly and commonly points to a triplet pairing. For the former, heavy fermion material, UPt3, a non-unitary bipolar state is the most possible candidate, whereas for the latter system, Sr2RuO4, determination of a precise pairing symmetry class, either unitary or non-unitary, is debated. 相似文献
10.
S V Suryanarayana B Gopala Krishna Ravichandra Gundakaram S Venkat Reddy 《Bulletin of Materials Science》1991,14(2):303-308
Samples with the nominal composition Bi2Sr2Ca1−x
Na
x
Cu2O
y
(x=0, 0·1, 0·2 and 0·3) were prepared by solid-state reaction of the individual compounds. X-ray diffraction patterns indicate
that the samples have a majority 2212 phase with 2223 also being present. From the DC four-probe resistance data, we have
observed that the furnace-cooled samples show metallic behaviour while the quenched samples show superconductivity up to 97
K. 相似文献
11.
近年来,由于磁性纳米粒子在实际应用中发挥越来越重要的作用,有关磁性纳米粒子的应用受到科学界广泛关注,特别是生物医学领域。由于磁性纳米Fe_3O_4粒子制作简单且晶体对细胞无毒,在生物医药领域大量应用,磁性纳米Fe_3O_4粒子主要通过表面包覆成为免疫磁性微球进行使用。简述了磁性纳米Fe_3O_4粒子的制备方法,重点综述了近些年磁性纳米Fe_3O_4粒子在生物医学上的应用,包括磁共振成像技术、磁分离技术、靶向药物载体技术、肿瘤热疗技术、造影剂技术,并且阐述了磁性纳米Fe_3O_4粒子的发展前景。 相似文献
12.
Y D Tembhurkar 《Bulletin of Materials Science》1996,19(1):155-159
Fe2O3 thin film was prepared using aqueous solution of FeCl3 by spray pyrolysis. The substrate temperature was 450°C. The lattice parametersa andc for different concentrations were calculated from X-ray diffraction study. Hexagonal structure of the Fe2O3 thin film was confirmed. Band gap values of Fe2O3 prepared from different concentrations were determined from optical transmission data. 相似文献
13.
The resistivity anomaly encountered in stoichiometric V2O3 is gradually suppressed with increasing density of cation vacancies. These observations are discussed in terms of related
findings reported in the literature.
Research supported by NSF-MRL Grant DMR 77-23798. 相似文献
14.
Marius Chirita Radu Banica Adrian Ieta Ioan Grozescu 《Particulate Science and Technology》2013,31(3):217-225
In this study, we develop an experimental procedure to synthesize hematite nanoparticles by hydrothermal decomposition of Fe-EDTA complex in the presence of hydrogen peroxide, starting from ferric ammonium sulfate and Na 4 EDTA as main precursors. The product was investigated by X-ray diffraction, scaning electron microscopy, dispersive X-ray spectroscopy, magnetic measurements, and UV-vis optical absorption measurements. The size of nanoparticles was determined to be 42 nm evaluated by XRD patterns using the Scherrer equation. This method allowed the formation of pure hematite nanoparticles with good and stable crystallographic characteristics. This procedure can be an effective method for synthesizing hematite nanoparticles exhibiting good crystallinity, stoichiometry, magnetic, and optical band gap properties. A possible mechanism for the formation of hematite nanocrystals was suggested. 相似文献
15.
《Journal of Experimental Nanoscience》2013,8(1):113-120
Nanocomposites composed of polypyrrole (PPy), graphite nanosheets (NanoGs), magnetite (Fe3O4) nanoparticles, have been successfully synthesised with a two-step process. First, we prepared NanoGs/Fe3O4 powder via wet chemical co-precipitation method. Next, pyrrole was polymerised in the suspension of NanoGs/Fe3O4 and then PPy/NanoGs/Fe3O4 nanocomposites were produced. The products were characterised by Fourier-transform infrared spectroscopy, Transmission electron microscopy, Thermogravimetric, conductivity and magnetisation analysis. The result showed that the conductivity of the PPy/NanoGs/Fe3O4 composites, compared with pure PPy, increased dramatically. And the saturation magnetisation of nanocomposites increased with the increase of the volume fraction of the Fe3O4 particles. In addition, according to the thermal gravimetric analysis, compared with PPy, nanocomposites exhibited enhanced thermal stability due to the introduction of NanoGs/Fe3O4. The PPy/NanoGs/Fe3O4 composites show potential applications in electric–magnetic shield materials. 相似文献
16.
We present DC magnetization data indicating a first-order phase transition in the vortex state of CeRu2, with the higher entropy phase exhibiting enhanced pinning. Minor hysteresis loops show evidence of supercooling of the higher
entropy phase as the phase boundary is crossed both isothermally as well as at constant field. These features are shown to
be absent across the Bragg-glass to vortex-glass transition in Bi2Sr2CaCu2O8. The supercooling is more persistent in the constant field case. 相似文献
17.
Ying Chen Yan-qing Dong Zhe Yan Dong Chen Yong Chen Lu-hui Wang 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(6):363-370
Carbonization of magnetic polymer microspheres is one of the methods for the preparation of magnetic carbon materials. Fe3O4 magnetic particle characteristics considerably influence the magnetic content and size distribution of magnetic polymer microspheres. The characteristics of Fe3O4 nanoparticles modified by oleic acid (OA) and undecylenic acid (UA) were analyzed by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, dynamic laser light scattering, thermogravimetry/differential thermogravimetry, vibrating sample magnetometer, and water contact angle. Fe3O4 nanoparticles modified by OA and UA are nearly spherical and exhibit superparamagnetism. Fe3O4 particle size and saturation magnetization are slightly influenced by the OA and UA composition. OA and UA both are chemically adsorbed onto Fe3O4 as bidentate chelates. OA shows easier adsorption onto Fe3O4 than UA. OA groups have an expanded arrangement on OA@Fe3O4, whereas UA groups have a condensed arrangement on UA@Fe3O4. Particle lipophilicity decreases and particle clustering increases with decreasing OA content and increasing UA content on OA-UA@Fe3O4 nanoparticles. 相似文献
18.
The influence of the Fermi surface anisotropy on the specific heat jump is studied for the p-wave superconductor with a gap function d = z^(k
x
± ik
y
) in connection with Sr2RuO4. It is shown that the normalized specific heat jump, C/T
c
, is reduced from its universal value, 1.43, in accordance with experimental findings. We show that this behavior fits well into our present understanding of the quasiparticle spectrum and the impurity effects. 相似文献
19.
The nitriding thermochemical treatment (NTT) is commonly used for steels. In this paper, the experimental conditions required
for NTT, and the influence of such treatments on the structure and hysteresis loops of Co74Fe8B12Si6 and Co74Fe4Mn4B12Si6 ribbons are reported. The results have been compared with those obtained with ribbons treated according to conventional thermal
treatment (CTT) as well. 相似文献
20.
The superconducting transition temperature, T
c
, of the impurity-free, intrinsic Sr2RuO4 is as high as 1.50 K. However, we recently showed that T
c
is remarkably increased up to 3 K in the Sr2RuO4–Ru eutectic system, in which plate-like microdomains of Ru metal are embedded in the primary-phase Sr2RuO4. The phase diagram of the anisotropic upper critical field of the 3-K phase indicates that H
c2 for the field parallel to the RuO2 plane is strongly suppressed at low temperatures. We argue that the reorientation of the Cooper-pair spin direction near the Sr2RuO4–Ru interface may be responsible for this suppression. In addition, we observed unusual hysteresis in the out-of-plane resistivity,
c
, at low temperatures and near H
c2, only when the field was applied parallel to the RuO2 plane. 相似文献