共查询到20条相似文献,搜索用时 0 毫秒
1.
Demet Korucu Ercan Ertekin İbrahim Belenli Semsettin Altindal 《Journal of Superconductivity and Novel Magnetism》2013,26(6):2165-2170
The dielectric loss (ε″) properties of MgB2 composites were investigated by using the conductance–voltage (G/w–V) measurements in the wide frequency and applied bias voltage range at four different temperature levels. Experimental results show that both G/w and ε″ are found strong functions of frequency and applied bias voltage for each temperature level. These changes in G/w and ε″ are considerably high especially at low frequencies and temperatures. The values of ε″ decrease exponentially with increasing frequency until 100 kHz and then become almost constant. Such behavior of G/w and ε″ shows that interfacial polarization is more effective especially at low frequencies. In addition, the current–voltage (I–V) characteristics were also evaluated for 100, 200, and 300 K, and the I–V curves for each temperature show linear behavior. Results indicate that the G/w–V measurements may be a useful tool to characterize the dielectric properties and conductivity of MgB2. 相似文献
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Y. Xue S. Asada A. Hosomichi S. Naher J. Xue H. Kaneko H. Suzuki T. Muranaka J. Akimitsu 《Journal of Low Temperature Physics》2005,138(5-6):1105-1115
We have performed powder X-ray diffraction of MgB2 superconductor between 10 and 300 K. Temperature dependence of integrated intensities of both (002) and (110) X-ray reflections shows a peak at around TC, superconducting transition temperature. The integrated intensity of the X-ray reflection is related to the phonon frequency through a Debye--Waller factor. Lattice parameters a and c show negative thermal expansions at low temperatures. The negative thermal expansion might be due to an electronic origin and not directly related to the superconducting transition. 相似文献
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Satoshi Abe Daisuke Takahashi Shigekazu Shiratori Hajime Yamamoto Shumsun Naher Bagum Haruhiko Suzuki Yoshichika Onuki 《Journal of Low Temperature Physics》1998,113(5-6):1061-1066
We have measured the magnetization of the heavy fermion compound CeRu
2
Si
2
at temperatures down to 300 K. We observed that the dc-magnetic susceptibility had the plateau due to the Pauli susceptibility between 50 mK and 2 K, and the upturn from this plateau toward lower temperatures. This excess susceptibility shows a Curie- Weiss behavior with a slight signature of saturation at the lowest temperature. This fact indicates that CeRu
2
Si
2
has the small residual magnetic moments in its ground state. 相似文献
5.
Pertti Hakonen Mikko Kiviranta Heikki Seppä 《Journal of Low Temperature Physics》2004,135(5-6):823-838
The interest in superconducting electronics working at millikelvin temperatures has increased during the past few years, and several novel devices and amplifiers utilizing mesoscopic Josephson junctions have been developed. We review the present status of a few of these devices, foremost the inductively-read superconducting Cooper pair transistor and the Bloch oscillating transistor. As a comparison, we review the status of dc SQUID devices which provide the traditional amplifier choice when approaching the standard quantum limit in ultra-sensitive measurements. In addition, we discuss a new type of current pump, the Sluice, in which modulation of Josephson energy is employed to produce large currents at high accuracy. These new developments continue the flourishing “Otaniemi tradition” in ultra-low-temperature physics and SQUID magnetometry for which Academician Olli V. Lounasmaa acted as the primus motor over three decades. 相似文献
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系统综述了MgB2超导纳米结构的制备方法,包括基于广义模板法的两步法或多步法、反应烧结法、基于电子束刻蚀技术、高温直接分解法、溶胶-凝胶法和混合物理化学气相沉积法等。总结了MgB2超导纳米结构的生长机理,并且评价了这些方法的优缺点。 相似文献
7.
A. S. Sidorenko V. I. Zdravkov V. V. Ryazanov M. Klemm S. Horn R. Tidecks C. Müller A. Wixforth 《Journal of Superconductivity and Novel Magnetism》2004,17(2):211-213
The origin of the resistive transition broadening for superconducting MgB2 films is investigated experimentally. The crucial role of two-dimensional weak and critical fluctuations is demonstrated. 相似文献
8.
Wei Zhou Jin Fang Xinyu Fang Bo Liu Yanchao Liu 《Journal of Superconductivity and Novel Magnetism》2018,31(4):951-957
In the applications of high-temperature superconductors (HTS), the HTS tapes are usually exposed to the external magnetic field with different orientations. The critical current and AC loss are affected by both the field amplitude and field angles due to the anisotropy of HTS tapes. In this work, we first introduce the experimental system to measure the magnetization loss in HTS tapes based on the calibration-free method. Then, we present the magnetization loss results in 4.8-mm-wide AMSC wire, 4-mm-wide SuperPower wire, 4-mm-wide SuNam wire, and 10-mm-wide Fujikura wire in a perpendicular applied field at 77 K. The field amplitude is up to 100 mT, and the frequency varies from 44.2 to 87.1 Hz. We also present the magnetization loss in AMSC wire, SuperPower wire, SuNam wire, and Fujikura wire at different field angles. The field angle varies from 10 to 90 ° in 10 ° steps. The loss reduction with the decreasing of the field angle shows the anisotropic property of HTS tapes. We finally plot the measured magnetization loss of the samples as a function of the magnetic field amplitude normalized by the field angle to verify an empirical formula. 相似文献
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Based on the angle-resolved photoemission spectra of single crystals, it is demonstrated that a couple of bands cross the Fermi energy in MgB2, which is in good agreement with band theory. The superconducting gap in this multiband system is carefully examined by Raman scattering spectroscopy with various polarizations. It has been revealed that the large gap (24k
B
T
c) that is typical for a clean limit s-wave superconductor is restricted to the -bands, while the gap on the -bands is much smaller (21.1k
B
T
c) and strongly affected by the impurity scattering, which gives a dirty limit behavior. This unusual two-gap behavior might be caused by the lack of interband scattering due to special separation of the - and -bands, as predicted by Mazin et al. 相似文献
12.
M. E. Yakıncı Y. Balcı M. A. Aksan H. İ. Adigüzel A. Gencer 《Journal of Superconductivity and Novel Magnetism》2002,15(6):607-611
Superconducting MgB2 polycrystalline samples have been fabricated under two different conditions in order to determine the effect of MgB4 phase. A series of samples was placed in an α-alumina container closed with a cup and fired under high purity argon gas. The other series of samples was placed in an α-alumina boot without any lid and fired under similar conditions. For the first series of samples, we have found pure MgB2 phase formation and a narrow transition width at 0.4 K. For the second series of samples, significant amount of MgB4 phase were formed and the T zero was decreased to 27 K. For both the group of samples magnetization hysteresis loops obtained at various temperature range and applied field up to 2 T. The best J cmag for the first series of samples was 1.9 × 105 A/cm2 at 10 K and 0 T, and for the second series of samples was 0.7 × 104 A/cm2 at 10 K and 0 T. 相似文献
13.
We present the formation of MgB2 coatings by simple and novel aerosol deposition technique which has a potential to escalate towards the fabrication of long superconducting tapes. The thin MgB2 coatings were produced by using pre-synthesized MgB2 powder. The ability of this technique to form a precursor powder in a thin film form has greatly reduced the intricacies involved in the synthesis of MgB2 by other techniques like hybrid physical chemical vapor deposition etc. The as-synthesized thin films were characterized by the x-ray diffraction technique to study the structural properties. The thin films were found to be x-ray amorphous in nature depicting the formation of frustrated structure which showed a superconducting transition onset at around 36 K. 相似文献
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X. X. Xi X. H. Zeng A. V. Pogrebnyakov A. Soukiassian S. Y. Xu Y. F. Hu E. Wertz Q. Li Y. Zhong C. O. Brubaker Z.-K. Liu E. M. Lysczek J. M. Redwing J. Lettieri D. G. Schlom W. Tian H. P. Sun X. Q. Pan 《Journal of Superconductivity and Novel Magnetism》2003,16(5):801-806
The recently discovered superconductor MgB2 with T c at 39 K has great potential in superconducting electronics. In this paper, we review the deposition techniques used for MgB2 thin films in the light of a thermodynamic study of the Mg-B system with the calculation of phase diagrams (CALPHAD) modeling technique. This thermodynamic study identifies a growth window in the pressure–temperature phase diagram, in which the magnesium pressure is very high for likely in situ growth temperatures. A Hybrid Physical–Chemical Vapor Deposition (HPCVD) technique that successfully achieves such a high Mg pressure is shown to produce in situ epitaxial MgB2 thin films with bulk superconducting properties. 相似文献
15.
Tsuyoshi Tamegai Zhixiang Shi Aswini Kumar Pradhan Hitomi Nakamura Ajay Kumar Ghosh Masashi Tokunaga Yoshihiko Takano Kazumasa Togano Hijiri Kito Hideo Ihara 《Journal of Low Temperature Physics》2003,131(5-6):1153-1157
Anisotropic superconducting properties of inter-metallic compounds MgB2, Y2PdGe3, and CaAlSi with AlB2 structure are studied by detailed angular dependent transport measurements. MgB2 and CaAlSi shows appreciable anisotropy of the upper critical field, H
c2, with mass anisotropy parameter =3 and 2, respectively, while Y2PdGe3 is almost isotropic. In-plane anisotropy of H
c2 in these hexagonal superconductors is very small, consistent with the prediction based on GL theory. 相似文献
16.
V. V. Bazarov J. ?wik D. Gajda P. N. Togulev N. M. Lyadov V. A. Shustov N. M. Suleimanov 《Journal of Superconductivity and Novel Magnetism》2012,25(6):1689-1694
Superconducting tapes from MgB2 and powders of magnetic Ni, Co, and non-magnetic Ti were fabricated by cold-processed powder-in-tube (PIT) method. The cupronickel was used as sheath material and no heat treatment was applied. The increasing of critical current was observed in the samples with additions of nickel and titanium. The microstructure and phase analysis of tape core was performed by X-ray diffraction spectroscopy. A direct correlation between type and amount of additives, and the critical current of the tapes has been observed. 相似文献
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由于具有超导转变温度(39K)较高,晶体结构简单,原材料成本低廉以及长线制备容易等一系列特点,金属间化合物二硼化镁( MgB2)超导体自2001年被日本科学家发现以来,引起人们广泛的关注,被认为是目前最有可能首先实现大规模工业应用的超导材料。尤其在制冷机工作温度(15~20 K)、较低磁场(1~2 T)条件下的医疗核磁共振成像仪( MRI)超导磁体应用上有着广泛的前景。本文主要围绕实用化 MgB2超导长线(带)制备研究而展开,重点回顾了近年来粉末套管法、连续粉末装管成型法及中心镁扩散法等MgB2超导线(带)材制备及加工方面的最新研究进展;同时综述了在 MgB2超导线带材工程临界电流密度性能改进方面的最新研究工作;最后,对近几年来 MgB2超导磁体及线圈等应用研究进展进行了回顾。 相似文献
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S. Safran J. ?ouc L. Rostila S. Brisigotti F. G?m?ry A. Gencer 《Journal of Superconductivity and Novel Magnetism》2011,24(1-2):437-441
Magnesium diboride (MgB2) is a good alternative for some of the conventional superconductors due to its low raw material costs and to its relatively simple production process. MgB2 wires have also been considered for AC applications. In this work, we present the magnetization AC loss results of a Ti-sheathed monofilament MgB2 wire when magnetic fields are applied perpendicular to the wire axis. Losses were measured by the calibration-free method using a lock-in amplifier at 144 Hz and also investigated theoretically in the same condition. Numerically estimated losses were compared to measured values. 相似文献
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M. Xu Y. Takano T. Hatano M. Kitahara D. Fujita 《Journal of Superconductivity and Novel Magnetism》2002,15(4):303-305
We report a simple method for the fabrication of reproducible, clean, and stable MgB2 superconducting tips. The quality of these tips has been verified by imaging the surface of a thin Au(111) film sample, using a low temperature scanning tunneling microscopy (STM). Using the MgB2 superconducting tip, high-quality semiatomically resolved STM surface images of the thin Au(111) film sample have been observed, which unambiguously indicates that the fabrication of relatively superconducting MgB2, suitable for use as STM tips, is feasible. 相似文献