Materials

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16 pages, 2447 KiB

Open AccessEditor’s ChoiceArticle

Dimensionality of the Superconductivity in the Transition Metal Pnictide WP

by Angela Nigro, Giuseppe Cuono, Pasquale Marra, Antonio Leo, Gaia Grimaldi, Ziyi Liu, Zhenyu Mi, Wei Wu, Guangtong Liu, Carmine Autieri, Jianlin Luo and Canio Noce

Materials 2022, 15(3), 1027; https://doi.org/10.3390/ma15031027 - 28 Jan 2022

Cited by 5 | Viewed by 2956

Abstract

We report theoretical and experimental results on the transition metal pnictide WP. The theoretical outcomes based on tight-binding calculations and density functional theory indicate that WP is a three-dimensional superconductor with an anisotropic electronic structure and nonsymmorphic symmetries. On the other hand, magnetoresistance [...] Read more.

We report theoretical and experimental results on the transition metal pnictide WP. The theoretical outcomes based on tight-binding calculations and density functional theory indicate that WP is a three-dimensional superconductor with an anisotropic electronic structure and nonsymmorphic symmetries. On the other hand, magnetoresistance experimental data and the analysis of superconducting fluctuations of the conductivity in external magnetic field indicate a weakly anisotropic three-dimensional superconducting phase. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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15 pages, 6304 KiB

Open AccessArticle

Modelling and Performance Analysis of MgB₂ and Hybrid Magnetic Shields

by Michela Fracasso, Fedor Gömöry, Mykola Solovyov, Roberto Gerbaldo, Gianluca Ghigo, Francesco Laviano, Andrea Napolitano, Daniele Torsello and Laura Gozzelino

Materials 2022, 15(2), 667; https://doi.org/10.3390/ma15020667 - 17 Jan 2022

Cited by 8 | Viewed by 2372

Abstract

Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB

_{2}

has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation [...] Read more.

Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB

_{2}

has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we report on a 3D numerical model based on a vector potential (A)-formulation, exploited to investigate the properties of superconducting (SC) shielding structures with cylindrical symmetry and an aspect ratio of height to diameter approaching one. To this aim, we first explored the viability of this model by solving a benchmark problem and comparing the computation outputs with those obtained with the most used approach based on the H-formulation. This comparison evidenced the full agreement of the computation outcomes as well as the much better performance of the model based on the A-formulation in terms of computation time. Relying on this result, the latter model was exploited to predict the shielding properties of open and single capped MgB

_{2}

tubes with and without the superimposition of a ferromagnetic (FM) shield. This investigation highlighted that the addition of the FM shell is very efficient in increasing the shielding factors of the SC screen when the applied magnetic field is tilted with respect to the shield axis. This effect is already significant at low tilt angles and allows compensating the strong decrease in the shielding ability that affects the short tubular SC screens when the external field is applied out of their axis. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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8 pages, 13519 KiB

Open AccessArticle

Drag Voltages in a Superconductor/Insulator/Ferromagnet Trilayer

by Paola Romano, Albino Polcari, Carla Cirillo and Carmine Attanasio

Materials 2021, 14(24), 7575; https://doi.org/10.3390/ma14247575 - 9 Dec 2021

Cited by 1 | Viewed by 2027

Abstract

The interaction between two spatially separated systems is of strong interest in order to study a wide class of unconventional effects at cryogenic temperatures. Here we report on drag transverse voltage effects in multilayered systems containing superconducting and ferromagnetic materials. The sample under [...] Read more.

The interaction between two spatially separated systems is of strong interest in order to study a wide class of unconventional effects at cryogenic temperatures. Here we report on drag transverse voltage effects in multilayered systems containing superconducting and ferromagnetic materials. The sample under test is a conventional superconductor/insulator/ferromagnet (S/I/F) trilayer in a cross configuration. S/F as well as S/N (here N stands for normal metal) bilayers in the same geometry are also analyzed for comparison. Current–voltage (I–V) characteristics measured at T = 4.2 K in the presence of a perpendicular magnetic field show strong peculiarities related to the interaction between the layers. The results are interpreted in terms of interaction effects between the layers. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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18 pages, 1714 KiB

Open AccessEditor’s ChoiceArticle

Superconducting Properties and Electron Scattering Mechanisms in a Nb Film with a Single Weak-Link Excavated by Focused Ion Beam

by Marlon Ivan Valerio-Cuadros, Davi Araujo Dalbuquerque Chaves, Fabiano Colauto, Ana Augusta Mendonça de Oliveira, Antônio Marcos Helgueira de Andrade, Tom Henning Johansen, Wilson Aires Ortiz and Maycon Motta

Materials 2021, 14(23), 7274; https://doi.org/10.3390/ma14237274 - 28 Nov 2021

Cited by 3 | Viewed by 2664

Abstract

Granularity is one of the main features restricting the maximum current which a superconductor can carry without losses, persisting as an important research topic when applications are concerned. To directly observe its effects on a typical thin superconducting specimen, we have modeled the [...] Read more.

Granularity is one of the main features restricting the maximum current which a superconductor can carry without losses, persisting as an important research topic when applications are concerned. To directly observe its effects on a typical thin superconducting specimen, we have modeled the simplest possible granular system by fabricating a single artificial weak-link in the center of a high-quality Nb film using the focused ion beam technique. Then, its microstructural, magnetic, and electric properties in both normal and superconducting states were studied. AC susceptibility, DC magnetization, and magneto-transport measurements reveal well-known granularity signatures and how they negatively affect superconductivity. Moreover, we also investigate the normal state electron scattering mechanisms in the Boltzmann theory framework. The results clearly demonstrate the effect of the milling technique, giving rise to an additional quadratic-in-temperature contribution to the usual cubic-in-temperature sd band scattering for the Nb film. Finally, by analyzing samples with varying density of incorporated defects, the emergence of the additional contribution is correlated to a decrease in their critical temperature, in agreement with recent theoretical results. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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9 pages, 2093 KiB

Open AccessEditor’s ChoiceArticle

Critical Current and Pinning Features of a CaKFe₄As₄ Polycrystalline Sample

by Armando Galluzzi, Antonio Leo, Andrea Masi, Francesca Varsano, Angela Nigro, Gaia Grimaldi and Massimiliano Polichetti

Materials 2021, 14(21), 6611; https://doi.org/10.3390/ma14216611 - 3 Nov 2021

Cited by 2 | Viewed by 2144

Abstract

We analyze the magnetic behavior of a CaKFe4As4 polycrystalline sample fabricated by a mechanochemically assisted synthesis route. By means of DC magnetization (M) measurements as a function of the temperature (T) and DC magnetic field (H) we study its critical parameters and pinning [...] Read more.

We analyze the magnetic behavior of a CaKFe4As4 polycrystalline sample fabricated by a mechanochemically assisted synthesis route. By means of DC magnetization (M) measurements as a function of the temperature (T) and DC magnetic field (H) we study its critical parameters and pinning features. The critical temperature T_c has been evaluated by M(T) curves performed in Zero Field Cooling-Field Cooling conditions. These curves show the presence of a little magnetic background for temperatures above T_c, as also confirmed by the hysteresis loops M(H). Starting from the M(H) curves, the critical current density J_c of the sample has been calculated as a function of the field at different temperatures in the framework of the Bean critical state model. The J_c(H) values are in line with the ones reported in the literature for this typology of samples. By analyzing the temperature dependence of the critical current density J_c(T) at different magnetic fields, it has been found that the sample is characterized by a strong type pinning regime. This sample peculiarity can open perspectives for future improvement in the fabrication of this material. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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22 pages, 4518 KiB

Open AccessEditor’s ChoiceArticle

Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB₂ Wires

by Daniel Gajda, Andrzej J. Zaleski, Andrzej J. Morawski, Malgorzata Małecka, Konstantin Nenkov, Matt Rindfleisch, Md Shahriar A. Hossain and Tomasz Czujko

Materials 2021, 14(18), 5152; https://doi.org/10.3390/ma14185152 - 8 Sep 2021

Cited by 1 | Viewed by 1747

Abstract

Annealing undoped MgB₂ wires under high isostatic pressure (HIP) increases transport critical current density (J_tc) by 10% at 4.2 K in range magnetic fields from 4 T to 12 T and significantly increases J_tc by 25% in range [...] Read more.

Annealing undoped MgB₂ wires under high isostatic pressure (HIP) increases transport critical current density (J_tc) by 10% at 4.2 K in range magnetic fields from 4 T to 12 T and significantly increases J_tc by 25% in range magnetic fields from 2 T to 4 T and does not increase J_tc above 4 T at 20 K. Further research shows that a large amount of 10% SiC admixture and thermal treatment under a high isostatic pressure of 1 GPa significantly increases the J_tc by 40% at 4.2 K in magnetic fields above 6 T and reduces J_tc by one order at 20 K in MgB₂ wires. Additionally, our research showed that heat treatment under high isostatic pressure is more evident in wires with smaller diameters, as it greatly increases the density of MgB₂ material and the number of connections between grains compared to MgB₂ wires with larger diameters, but only during the Mg solid-state reaction. In addition, our study indicates that smaller wire diameters and high isostatic pressure do not lead to a higher density of MgB₂ material and more connections between grains during the liquid-state Mg reaction. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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18 pages, 7271 KiB

Open AccessArticle

Experimental and Numerical Analysis of High-Temperature Superconducting Tapes Modified by Composite Thermal Stabilization Subjected to Thermomechanical Loading

by Eva Cuninková, Marcela Pekarčíková, Michal Skarba, Jozef Krajčovič and Matej Pašák

Materials 2021, 14(13), 3579; https://doi.org/10.3390/ma14133579 - 26 Jun 2021

Cited by 4 | Viewed by 1872

Abstract

The strain behavior of SiC/Stycast 2850 FT composites under thermomechanical loading using a finite element analysis (FEA) was studied. These composites can serve as thermal stabilizers of high-temperature superconducting (HTS) tapes during limitation event in resistive superconducting fault current limiter (R-SCFCL) applications. For [...] Read more.

The strain behavior of SiC/Stycast 2850 FT composites under thermomechanical loading using a finite element analysis (FEA) was studied. These composites can serve as thermal stabilizers of high-temperature superconducting (HTS) tapes during limitation event in resistive superconducting fault current limiter (R-SCFCL) applications. For this purpose, the thermomechanical properties of four composite systems with different filler content were studied experimentally. The FEA was calculated using an ANSYS software and it delivered useful information about the strain distribution in the composite coating, as well as in particular layers of the modified HTS tapes. The tapes were subjected to bending over a 25 cm core, cooled in a liquid nitrogen (LN2) bath, and finally, quenched from this temperature to various temperatures up to 150 °C for a very short time, simulating real limitation conditions. The outputs from simulations were also correlated with the experiments. The most promising of all investigated systems was SB11-SiC20 composite in form of 100 µm thick coating, withstanding a temperature change from LN2 up to 120 °C. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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8 pages, 3852 KiB

Open AccessArticle

Measurement of Electrical Properties of Superconducting YBCO Thin Films in the VHF Range

by Yakir Dahan, Eldad Holdengreber, Elichai Glassner, Oz Sorkin, Shmuel E. Schacham and Eliyahu Farber

Materials 2021, 14(12), 3360; https://doi.org/10.3390/ma14123360 - 17 Jun 2021

Cited by 6 | Viewed by 2405

Abstract

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is [...] Read more.

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is required for derivation of the exact configuration of the MS. A theoretical model is presented, from which an expression for the attenuation of a MS line can be derived. Accordingly, simulations were performed, and an optimal resonator for the VHF range was designed and implemented. Production constraints of YBa₂Cu₃O₇ (YBCO) limited the diameter of the sapphire substrate to 3″. Therefore, a meander configuration was formed to fit the long λ/4 MS line on the wafer. By measuring the complex input reflection coefficients of a λ/4 resonator, we extracted the quality factor, which is mainly affected by the dielectric and conductor attenuations. The experimental results are well fitted by the theoretical model. The dielectric attenuation was calculated using the quasi-static analysis of the MS line. An identical copper resonator was produced and measured to compare the properties of the YBCO resonator in reference to the copper one. A quality factor of ~

6 \cdot 10^{5}

was calculated for the YBCO resonator, three orders of magnitude larger than that of the copper resonator. The attenuation per unit length of the YBCO layer was smaller by more than five orders of magnitude than that of the copper. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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