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We have investigated the electrical transport and magnetic properties of Eu x Ca 1 − x Fe 2 As 2 (ECFA) (0 ≤ x ≤ 1) at ambient and under high-pressure. Temperature dependence of resistance shows a distinct anomaly at T SDW ∼ 165 − 190 K due to the spin density wave (SDW) transition. Initially, T SDW increases rapidly with x up to 0.45, and then more slowly at higher x until it saturates at T SDW ∼

The first systematic study of the nano-scale periodic local density of states (LDOS) and the inhomogeneous gap distributions for the Pb doped Bi 2 Sr 2 Ca 2 Cu 3 O 10 + y (PbBi2223) microcrystals was carried out using the low-temperature scanning tunneling microscopy/spectroscopy. The spatially inhomogeneous gap distributions with patchy structures of several nm size reveal the average gap magnitude

Understanding the mechanisms that limit the current transport in granular iron-based superconductors is necessary to unlock their potential for magnet applications. This paper reports the transport critical current surface I C ( T,H ) of powder-in-tube Ag/Ba 1−x K x Fe 2 As 2 tapes densified by flat rolling and uniaxial hot pressing. We investigate the amplitude of the isothermal- I C ( H )-curve magnetic

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ReBCO superconducting cables have the potential to enable compact thermonuclear fusion reactors that operate at magnetic fields exceeding 20 T and allow operation at temperatures far exceeding the boiling point of liquid helium, potentially allowing for demountable magnets. Normal zone detection remains a challenge, and while novel quench detection techniques are an active area of research, few are

We report on the growth of NdFeAs(O,H) epitaxial thin films on MgO (001) substrates and their electrical transport properties. The maximum carrier density of the NdFeAs(O,H) films was more than twice as large as that of our NdFeAs(O,F) films. This enabled us to investigate the physical properties of heavily electron doped NdFeAsO, which could not be achieved with NdFeAs(O,F). The irreversibility field

We report on the effects of 3.5 MeV proton irradiation on single crystals of the magnetic superconductor EuFe 2 (As 1 − x P x ) 2 , investigated at microwave frequencies by a coplanar waveguide resonator technique. We studied the relative strength of the two collective phenomena by analyzing the dependence of their onset temperatures on different perturbations: magnetic fields and structural disorder

The effect of microstructure control on intergranular critical current density ( J c ) was evaluated using Co-doped Ba122 as a model material. Polycrystalline bulk samples were prepared by sintering mechanically alloyed powder prepared by planetary ball milling. Between low and intermediate milling energy, refinement of grain size, improvement in the uniformity of structure and composition, and a threefold

We report on the introduction of columnar defects in Ba 1− x K x Fe 2 As 2 and BaFe 2 (As 1− x P x ) 2 single crystals via 1.2 GeV Pb irradiation. Scanning transmission electron microscopy analysis proves the formation of continuous defects along the ion tracks, with a diameter of about 3 nm, and a planar density compatible with the irradiation fluence. The twofold role of such defects, i.e. as pair

When exposed to time-dependent magnetic fields, REBCO Roebel cables generate AC loss resulting from both magnetic hysteresis and induced inter-strand coupling currents. Until now, the AC loss has been computed in a two-dimensional approximation assuming fully coupled or decoupled strands, and a finite inter-strand resistance could be simulated only with three-dimensional models. In this work, we propose

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Any theory of electron-phonon mediated superconductivity requires knowledge of the full phonon spectrum ##IMG## [http://ej.iop.org/images/0953-2048/33/9/094009/sustab953fieqn1.gif] {${\alpha ^2}\left( \omega \right) \cdot F\left( \omega \right)$} in order to calculate superconducting transition temperature, T c . However, there is currently no experimental technique for measuring ##IMG## [http://ej

We established a 3D coupled model to study the electromagnetic-thermal behaviors of a levitation system containing a bulk high-temperature superconductor (HTS) with a cuboid slot under the nonuniform magnetic field due to the movement of a permanent magnet (PM), analysing the influences of the geometrical parameters of the slot and inclination angle on the electromagnetic-thermal behaviors, giving

High T c superconducting (HTS) DC cable is a promising solution for large-scale power transmission over long distance. However, the refrigeration system for HTS cable is indispensable but undesirable. Considering that LNG (liquid natural gas) is now one kind of clean energy that is used more and more widely, it is possible to integrate HTS cable and LNG transportation into a single pipeline, resulting

This paper deals with the fabrication and performance testing of a prototype machine for the world’s first implementation of a new type high-temperature superconducting rotating machine (HTSRM), which is charged and operated by the application of a contactless superconducting excitation technique with a rotary-type HTS flux pump based on a permanent magnet. Although this type of flux pump has been

Iron-chalcogenide FeSe x Te 1− x (Fe(Se,Te)) superconductors have attracted a great deal of interest in both fundamental physics and potential applications. While Majorana zero-modes hosted by the Fe(Se,Te) superconductors hold great promise for topological quantum computing, low-anisotropy and very high upper critical fields make Fe(Se,Te) an excellent candidate for high-magnetic-field and energy

A high density CaKFe 4 As 4 bulk sample was successfully synthesized using a spark plasma sintering (SPS) technique. The density of the synthesized sample was 5.02 g cm −3 , corresponding to 96.2% of the theoretical density of CaKFe 4 As 4 . Moreover, a reasonably high Vickers hardness of 1 GPa was measured. The electrical resistivity of the SPS bulk sample was as low as approximately 600 μ Ω cm at

We investigated the effect of different sintering processes on Ag–added FeSe 0.94 superconducting wires. After applying different sintering procedures, we successfully obtained zero resistivity, at 350 °C for 100 h and at 700 °C for 1 h, in Ag–added FeSe 0.94 superconducting wire produced using the ex-situ powder-in-tube method. The crystal structure of both wires is mainly composed of the tetragonal

Bulk high-temperature superconductors (HTSs) that act as a trap field magnet establish a novel type of magnetic field source, which is significantly different from that of a permanent magnet or solenoid; therefore, they can be potentially used in magnetic-force-based applications. However, the primary issues related to the commercial use of the bulk HTS technology are established on the enhancement

In bulk high-temperature superconductors, Ag is usually used as an additive thus improving mechanical performance. In MgB 2 doped with Ag, the Ag reacts with Mg, forming Mg–Ag phases acting as a vortex pinning medium. In this work, we analyze the electromagnetic and pinning properties of bulk MgB 2 doped with 1 wt% MgB 4, 4 wt% Ag, and 1 wt% Dy 2 O 3 , prepared at the Shibaura Institute of Technology

The fundamental harmonic of the AC magnetic susceptibility of a Fe(Se,Te) single crystal iron based superconductor has been studied at different AC field amplitudes and frequencies with and without a superimposed DC magnetic field with the aim of analyzing its superconducting properties that can be also suitable for power applications such as the critical current density and the pinning energy in AC

MgB 2 superconducting wires made using a Mg infiltration method have reached a higher performance than either in-situ or ex-situ mixed powder based routes. Indeed, very high layer J c coupled with whole-strand J e (critical current per total strand cross section) exceeding 10 4 A cm −2 at 4.2 K, 10 T have been found for monocore MgB 2 wires. However, previous multicore infiltration route wires have

Compact narrowband high-pole dual-band high-temperature superconducting (HTS) bandpass filters (BPF) have been developed that use newly developed stub-loaded double-folded microstrip resonators. The resonators have a weak coupling property that enables the distance between resonators to be reduced and that suppresses unwanted nonadjacent coupling. Moreover, it enables independent control of the resonant

RE Ba 2 Cu 3 O 7− x ( RE BCO, RE = rare earth) compounds with different single RE elements were grown via TFA-MOD (metal-organic deposition of trifluoroacetates) to clarify their T c values when grown by the same preparation method and their processing windows; here: the crystallisation temperatures at a constant process gas composition ( p O 2 , p H 2 O). We focussed on the lanthanides ( Ln ) Nd,

YBa 2 Cu 3 O 7–x (YBCO) films grown by metal-organic decomposition (MOD) are promising candidates for the production of high performance high temperature superconductors (HTS) tapes. Moreover, artificial pinning centers (APCs) introduction proved to be a powerful tool for the improvement of transport properties in YBCO films. Along with the widely employed pinning strategies, such as the introduction

We report recent developments in the scale-up of symmetric RE -Ba-Cu-O ( RE BCO) tapes with 15–22 μ m thick substrates. Using these symmetric RE BCO tapes, we fabricated up to 10 m long, symmetric tape round (STAR™) RE BCO wires, less than 2 mm diameter, using 1.02 mm and 0.81 mm diameter copper formers. The critical current of the long STAR™ wires made in lengths of 2–10 m ranges from 465 A to 564

The screening current induced in superconductors can passively shield external magnetic fields and hence provide a noise free environment for precision sensors and instruments. This paper presents a novel design employing artificial joint-free REBCO (REBa 2 Cu 3 O 7-x , RE: rare earths) coils which can economically extend the field shielding space for larger instruments, e.g. clinical equipment. We

Superconducting joints of Ba 0.6 K 0.4 Fe 2 As 2 (BaK-122) tapes were fabricated by a simple cold-pressing method. The interfaces of the superconducting cores were prepared by two different methods; (i) peeling off a part of the Ag sheath (PO joint) and (ii) angle polishing of one edge of each tape (AP joint). For the PO joint, a critical current ratio (CCR = I c joint / I c tape , where I c tape and

The poor reproducibility of intergrain critical current density J c in Fe-based superconductors is often believed to result from uncontrolled grain boundary (GB) connectivity degraded by extrinsic factors such as the local or global impurity concentration or GB porosity or cracks. Earlier we found that Ba and K can appear as oxide impurities at GBs, along with GB-wetting FeAs. In this study, we evaluated

Superconducting quantum interference devices (SQUIDs) are a key component of new superconducting gravity instruments (SGIs). They have a higher displacement detection resolution than traditional methods. However, owing to the finite system slew rate, flux jump occurs when SQUIDs are disturbed by high-frequency electromagnetic signals, which makes the SGI incapable of long-term measurement and creates

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Dynamic loss is an essential parameter to consider for the design of high temperature superconducting (HTS) synchronous machine windings. For aerospace electric propulsion systems, the fundamental frequency component and harmonics in electric machines can attain kHz level because of the high rotating speed. However, for HTS coated conductors (CC), the existing definition of dynamic loss only considers

We performed systematic AC susceptibility and magnetic moment measurements to investigate the vortex dynamics and pinning in ##IMG## [http://ej.iop.org/images/0953-2048/33/8/084009/sustab9aa5ieqn1.gif] {$EuRbFe_4As_4$} single crystals as a function of temperature, frequency, and DC magnetic field. The vortex solid-liquid line was determined, and it can be fitted well with ##IMG## [http://ej.iop.or

Safe operation of large superconducting magnets wound from high-temperature superconductors (HTS) requires reliable detection of the onset of a quench. A novel method to integrate optical fibers and voltage wires within the core of multi-tape HTS CORC ® wires has been developed that allows real time monitoring of local changes in strain, temperature and of the superconducting state of the magnet windings

The quench characteristic is a critical issue for the application of superconducting cable. In order to study the process of the quench behavior in the cable accurately, a four-dimensional (4D) quench model for quasi-isotropic superconducting cable was developed and presented, in this paper. We first consider that the materials of the cable are in perfect thermal contact with the neighboring ones,

Superconducting properties of the Fe(Se,Te) system are directly related to its microstructure. However, in the framework of a not well assessed phase diagram, a large spread of chemico-physical and functional properties is reported for compounds characterized by similar overall chemical compositions. This is in particular observed in materials produced by melting routes, where chemical inhomogeneities

Flux avalanches induced from thermomagnetic instability are crucial challenges for the application of superconducting thin film devices. In this paper, flux avalanches in a type-II superconducting thin film exposed to a transient AC magnetic field are numerically simulated by solving the coupled nonlinear Maxwell’s equations and the heat diffusion equation based on the fast Fourier transform (FFT)

The epitaxial growth of Zr-doped CeO 2 (CZO) films by chemical solution deposition (CSD) on single crystal substrates such as Al 2 O 3 , SrTiO 3 and Y 2 O 3 -stabilized ZrO 2 (YSZ) and their use as buffer layers for Fe(Se,Te) film growth are reported. The growth of 30 nm thin CZO films is mostly dominated by dewetting issues, leading to highly incomplete substrate coverage due to the strong tendency

Many high-temperature superconductor (HTS) applications require superconducting cables with high currents while operating in an alternating magnetic field. HTS cables should be composed of numerous superconducting tapes to achieve the required current capacity. Alternating current and magnetic fields cause AC losses in such cables and can provoke conductor instability. AC losses and contact resistances

We solve several applied superconductivity problems using the series in Chebyshev polynomials. Although this method may be less general than the usually employed finite element methods, accuracy of the obtained solutions is often much higher due to the very fast convergence of the Chebyshev expansions. First, as an introduction, we consider the thin strip magnetization and transport current problems

The pinning properties of GdBa 2 Cu 3 O 7-δ (GdBCO) films fabricated by the reactive co-evaporation deposition and reaction (RCE-DR) process were very sensitive to the post-annealing temperature in a reduced oxygen atmosphere. For this study, as-grown GdBCO coated conductors (CCs) were post-annealed at the temperatures ranging from 450 to 750 °C in the oxygen pressure ( P O 2 ) of 300 mTorr, and subsequently

A novel magnetizing technique for permanent magnets (PMs) embedded in interior permanent magnet (IPM) motors has been proposed as a safer and more effective process than the conventional processes using copper pulse-coils. In the new process, the high temperature superconducting (HTS) bulk magnet, emitting an intense magnetic field of over 3 T, was employed to activate the rotor and PMs inside. A magnetic

A high-temperature superconductor (HTS) bandpass filter with special asymmetric cul-de-sac units (SACUs) is introduced and a compact low-radiating microstrip resonator is suggested for the filter realization. Such a filter is capable of providing better selectivity and higher out-of-band rejection and hence a decrease in adjacent-channel interference, which is of critical importance for mobile communication

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Since the discovery of high temperature superconducting (HTS) material, HTS maglev with the characteristics of self-stabilization and zero magnetic drag, has shown excellent potential for future transportation applications. However, this stability characteristic of HTS maglev is difficult to fully ensure in a spatial position, because of the magnetic flux flow and creep of the HTS bulk. Hence, to study

The current-limiting performance of the dc resistive-type superconducting fault current limiter (dc R-SFCL) is vital to the reliability in the high voltage dc current (HVDC) transmission system. It is expensive and difficult to utilize the discharging process of the precharged dc capacitor to evaluate the current-limiting performance. In this paper, a R-Q curve based evaluation method for current-limiting

The no-insulation (NI) winding method is an effective technique for winding coils from high- ##IMG## [http://ej.iop.org/images/0953-2048/33/8/08LT01/sustab9688ieqn1.gif] {$T_{\rm c}$} superconductors (HTS). NI coils are electrically and thermally robust due to their ability to radially bypass current away from the fragile superconducting path when necessary. This avoids stored magnetic energy being

Secondary CLIQ is a quench protection method for protecting high-field accelerator magnets that involves charged capacitors into secondary normal-conducting coils that are magnetically coupled to the superconducting coils. The resulting coupling losses quickly brings the magnet to normal state and safely discharges it. No direct electrical or thermal link is required between the primary and secondary

This paper presents the properties of cables made of thin MgB 2 wires with different sheaths manufactured by IMD process. Strong effect of the outer sheath on the J e ( B ) performance was observed and the best properties were obtained for the strongest Cu sheath. It was found that the transversal and longitudinal cables uniformity affects the critical currents in MgB 2 wires made by IMD considerably

REBa 2 Cu 3 O 7−δ (REBCO) composite tapes are candidate conductors for future accelerator magnets. Given that REBCO is a brittle oxide film, stress/strain management is important in the mechanical design of a magnet. Therefore, the strain state of a superconducting film should be predicted under various operating conditions. A quantum beam is a useful tool in evaluating the strain state of a superconducting

With the development of high-temperature superconducting (HTS) materials, several HTS applications are been proposed and developed. Due to the HTS non-linear and non-homogeneous electromagnetic characteristics, the optimization process of an HTS system is a complex task requiring high computational time and resources. Within this context, this paper focuses on the comparison of HTS models for a fast

A trapped field of B T = 1.61 T was experimentally achieved at the central surface of an MgB 2 bulk composite (60 mm in diameter and 20 mm in height) at 20 K by double pulsed-field magnetization (PFM) using a split-type coil. The composite bulks consisted of two MgB 2 ring bulks sandwiched by thin copper ring plates, which were then stacked, and a soft iron yoke cylinder was inserted in the central

We present results on the in-field critical current ( I c ) performance of 4.0 μ m thick REBCO film with 15% Hf addition with fields up to 31.2 T and field orientations in the B║ab plane and B║c axis. Unlike the behavior at B║c, the critical current at B║ab is only very weakly dependent on field, decreasing from self-field to 31.2 T by only 22%, i.e. from the self-field value of ∼7700 A/4 mm width

In high power density superconducting motors, superconducting tapes are usually stacked and connected together at terminals to improve the current capacity. When a parallel sinusoidal magnetic field is applied on this partially coupled stack, the coupling current is induced and causes additional coupling loss. Usually 3D modeling is needed to calculate the coupling loss but it takes too much computing

We investigate the physics of planar annular Josephson tunnel junctions quenched through their transition temperature in the presence of an external magnetic field. Experiments carried out with long Nb / Al - AlOx / Nb annular junctions showed that the magnetic flux trapped in the high-quality doubly-connected superconducting electrodes forming the junction generates a persistent current whose associated

Electronic transport measurements were carried out on c -axis oriented epitaxial FeSe thin films in static magnetic fields up to 14 T parallel to the crystallographic c -axis and parallel to the ab -plane. The temperature dependence of the upper critical fields ##IMG## [http://ej.iop.org/images/0953-2048/33/7/075011/sustab9001ieqn1.gif] {$B_{c2}^c$} and ##IMG## [http://ej.iop.org/images/0953-2048/

Mechanical failure is one of the most significant challenges for the application of bulk superconductors acting as trapped field magnets. In this paper, a numerical simulation framework based on the coupled H-formulation for electromagnetics of superconductors and the phase-field fracture model for solids is proposed and implemented to simulate the crack nucleation and propagation within bulk superconductors

The Rashba superconductor, in which spin-splitting bands become superconducting, is fascinating as a novel superconducting system in low-dimensional systems. Here, we present the results of in-situ transport measurements on a Rashba-type surface state of the striped incommensurate (SIC) phase of a Pb atomic layer on Ge(111) surface with additional Pb islands/clusters on it. We found that two-step superconducting

The longitudinal thermal transport properties of composite multi-filamentary iron-based superconducting tapes are studied in magnetic fields up to 9 T. The Cu/Ag tape exhibits the highest thermal conductivity κ(4.2 K) = 440 W m −1 K −1 at 0 T, which remains above 100 W m −1 K −1 at 9 T. After applying different alloys as the outer sheath, the overall thermal conductivity is considerably decreased.