Thickness Of Superconducting Film Research Articles

Giant demagnetization effects induced by superconducting films

We show that a ferromagnetic (F) slab with the in-plane magnetization sandwiched between two superconducting (S) films experiences strong demagnetization effect due to the Meissner screening of the stray magnetic field by superconductors. In the extreme case, the transition of the S film from normal to the superconducting state can switch the demagnetization factor from 0 to 1, which is in a sharp contrast with the S/F bilayers where such transition affects the magnetic field inside the F film only slightly. The giant demagnetization effect is shown to be qualitatively robust against the decreasing superconducting film thickness and may provide a hint toward the explanation of the anomalously large ferromagnetic resonance frequency shift recently observed for the S/F/S structures [Golovchanskiy et al., Phys. Rev. Appl. 14, 024086 (2020)].

Possibilities of the Master Mask Method in Analysis of Characteristics of Planar HTSC Structures Depending on Superconducting Film Thickness

In contrast to traditional methods for obtaining planar superconducting structures based on YBCO films, in which the topology is formed by etching or ion implantation, the topology in the master mask (MM) method is set at the initial stage of structure preparation, during the MM formation, and the YBCO deposition is the final stage. The superconducting elements of the structure are formed in MM windows, and insulating regions appear between them. Having fixed the topology of superconducting bridges at the MM formation stage, we measured their characteristics depending on the YBCO film thickness, performing deposition cycles sequentially. After each YBCO deposition cycle, we measured the structure parameters of the film as well as the critical temperature and current in the bridges, including the bridges with the Josephson junctions formed on a bicrystal substrate.

Electrophysical Characteristics of Y Based Superconducting Composite.

The research in this paper was conduced with the purpose of developing a electrophoretic deposition process technology, and finding out an optimization method for fabrication of YBCO superconductor thick film tapes by using superconducting YBCO powder, and applying the electrophoresis technique. Through the development of an electrodeposition process, this study tried to determine an optimization method to improve the density and orientation of powder particles and a way to obtain a uniform surface to overcome cracking and porosity problems possibly occurring in the drying and heat-treatment processes. In this study, the electrophoretic deposition technique, which is to align and maintain particles toward the backside of the C axis of Ag substrates in a tape form, through excitation of powder particles with AC electric current, and then to perform deposition under a condition, was applied to the electrophoretic deposition process.

Inhomogeneous Spin Diffusion in Thickness-Controlled La 0 . 6 7 Sr 0 . 3 3 MnO 3 /YBa 2 Cu 3 O 7 − δ /La 0 . 6 7 Sr 0 . 3 3 MnO 3 Trilayers

La0.67Sr0.33MnO3/YBa2Cu3O7 − δ /La0.67Sr0.33 MnO3 (LSMO/YBCO/LSMO) trilayers are prepared on single-crystal LaAlO3 (LAO) substrates by pulsed laser deposition (PLD) with the thicknesses of LSMO layers fixed at 50 nm, and the thickness of YBCO sandwich varied from 10 to 40 nm. X-ray diffraction (XRD) and pole figure measurements disclose that all the trilayers are c-oriented and there is little change in the textures of YBCO layer for both in-plane and out-of-plane. Based on inductive, transport, and magnetic measurements, obvious suppression of superconductivity with a decrease in YBCO thickness is observed, particularly at thickness below 20 nm. Importantly, there are great disparities in the superconducting transition temperature (T c) and transition width (ΔT c) values for both inductive and transport measurements. The T c values from an inductive method are much smaller than those from transport measurements, with ΔT c in the opposite direction. The results are explained by the nonuniform diffusion of spin-polarized quasiparticles due to the comparable length scales of the spin diffusion length and the superconducting film thickness.

Suppressed Superconductivity Induced by Spin Diffusion Effect in La0.67Sr 0.33MnO 3/YBa 2Cu 3 O 7−δ Bilayers

An elaborately designed bilayer consisting of epitaxial YBa 2Cu 3O7−δ (YBCO) and La 0.67Sr 0.33MnO 3−δ (LSMO) films is prepared on a single crystal SrTiO 3 (STO) substrate by pulsed laser deposition (PLD), with respect to the investigation into the influence of spin diffusion on superconductivity. Structural measurements reveal that the present bilayer has good textures of both in-plane and out-of-plane as well as perfect superconducting layer without residual stress. Nevertheless, obviously suppressed superconductivity is found in the bilayer, as evidenced by the reduced superconducting transition temperature and critical current density. It is believed that the suppressed superconductivity arises from the spin diffusion effect due to the comparable length scales of the spin diffusion length and the superconducting film thickness.

Electro-Physical Properties of Superconducting Ceramic Thick Film Prepared by Partial Melting Method

BiSrCaCuO superconductor thick films were prepared at several curing temperatures, and their electro-physical properties were determined to find an optimum fabrication conditions. Critical temperatures of the superconductors were decreased with increasing melting temperature, which was related to the amount of equilibrium phases of the superconducting materials with temperature. The critical temperature of BiSrCaCuO bulk and thick film superconductors were 107 K and 96 K, respectively. The variation of susceptibility of the superconductor thick film formed at 950 degrees C had multi-step-type curve for 70 G externally applied field, whereas, a superconductor thick film formed at 885 degrees C had a single step-type curve like a bulk BiSrCaCuO ceramic superconductor in the temperature-susceptibility curves. A partial melting at 865 degrees C is one of optimum conditions for making a superconductor thick film with a relatively homogeneous phase.

Hg0.8Re0.2Ba2Ca2Cu 3O8.8 thick film produced by Laser Ablation

This paper describes the development of Hg0.8Re0.2Ba2Ca2Cu 3O8.8 thick film prepared with a precursor Ba2Ca2Cu3O5+d thick film, which was layered by Laser Ablation technique on PrBa2Cu3O7 substrate. The precursor thick film was thermally treated under mercury atmosphere using an encapsulate quartz tube technique. DC critical current measurements below T C determined the thick film superconductor current critical density as a function of temperature. The general behavior of the critical current density as a function of temperature confirms that the (Hg,Re)-1223 thick film has junctions type classified as superconducting-insulate-superconducting (SIS). After the critical current test the superconductor thick film has not shown any degradation or stoichiometry loss and its critical temperature has not changed after the test. Taken into account the critical current value of thick film as compared with the bulk sample, it was suggested that the procedure described here can be applied to build most electronic-type applications based on (Hg,Re)-1223 ceramic thick film.

Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

The superconducting properties ofPb82Bi18 alloy films deposited on ferromagnetic nanowire arrays have been investigated.Ferromagnetic Co or Ni nanowires are first electroplated into the columnarpores of anodic aluminum oxide (AAO) membranes. SuperconductingPb82Bi18 films are then quench condensed onto the polished surface of the AAOmembranes filled with magnetic nanowires. A strong dependence of thePb82Bi18 superconducting properties on the ratio of the superconducting film thickness to themagnetic nanowire diameter and material variety was observed.

ChemInform Abstract: Metal Dopants in Bi-Pb-Ca-Sr-Cu-O High-Tc Superconductor Thick Films Prepared by Melt Solidification.

Metal-doped superconductor thick films Bi1.6Pb0.4M0.1 Ca2-Sr2Cu3Ox (M = V, Nb, Mo, In, Sn, Sb, and W) were prepared using a melt–solidification procedure. The optimum heat-treatment temperature Topt was observed in all the films with different dopants; Topt was related to the temperature at which a partial melting of the films occurred as determined by differential thermal analysis. The dopants in the melt-solidified films lower the partial melting temperature and thus lower Topt for the formation of the 110 K phase.

Fourier Transform Domain Analysis of High T c Superconducting Rectangular Microstrip Patch over Ground Plane with Rectangular Aperture

A rigorous full-wave analysis in the Fourier transform domain is carried out in order to obtain the resonant frequencies and half-power bandwidths of the high Tc superconducting rectangular microstrip patches over ground planes with rectangular apertures. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. This impedance is determined by using London’s equation and the two-fluid model of Gorter and Casimir. The validity of the solution is tested by comparison of the computed results with previously published data. Variations of the resonant frequency with the high Tc superconducting film thickness are presented. Results showing the effect of the temperature on the resonant frequency and half-power bandwidth of the superconducting microstrip antenna with a rectangular aperture in the ground plane are also given. Finally, a comparison between the efficiency of two antennas is presented. For the first antenna, YBCO patch with YBCO ground plane are considered. For the second antenna, the patch and the ground plane are with copper.

Investigation of miniature CO2 gas sensor based on NASICON

A miniature CO2 gas sensor based on NASICON (sodium super ionic conductor) thick film was fabricated. The solid-electrolyte NASICON material was synthesized through an inorganic-reagent-based sol-gel method. The resulting materials were characterized by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). NASICON paste was coated on a piece of alumina substrate attached to a platinum heater. Li2CO3-BaCO3 binary carbonate in molar ratio 1 : 1.5 was utilized as the sensing electrode. Within a wide range of CO2 volume ratio concentration from 500 to 5000 ppm, the output electromotive force (EMF) of the sensor followed Nernst equation well at high working temperature. The response and recovery times were 20 and 58 s, respectively. This miniature CO2 gas sensor possessed extra merits such as low power consumption, miniaturized framework, and easy fabrication.

Fabrication of Bi2Sr2CaCu2O x and Bi2Sr2Ca2Cu3O x Superconductor Thick Films by Using Cu-Free Precursors on Ni Substrates

We studied the formation of Bi2Sr2CaCu2O x (Bi-2212) and Bi2Sr2Ca2Cu3O x (Bi-2223) thick films in a heat treatment process of the Ni-sheathed Bi-Sr-Ca-Cu-O (BSCCO) system. Cu was electrodeposited initially on the Ni substrates (Cu/Ni). Well-oriented Bi-2212 superconductor thick films were formed successfully on Ni tapes by liquid reaction between Cu-free precursors and Cu/Ni tapes. However, only a small amount of Bi-2223 was formed. Thick films were prepared by screen-printing with Bi2O3, SrCO3, and CaCO3 powders on Cu/Ni tapes and heat treating them. Heat treatment was performed in the temperature range of 750–850°C in a tube furnace for several minutes to hours. The phases and the microstructures of the high temperature superconductor thick films were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Electrical properties were examined by the standard four-probe method. At the heat treatment temperature, the specimens were in a partially molten state during reaction between the oxidized copper layer and the screen-printed precursors on the Cu/Ni tapes.

Effects of thickness on the grain alignment and Jc properties of (Hg 0.8Re 0.2)Ba 2Ca 2Cu 3O x superconductor thick films

(Hg 0.8Re 0.2)Ba 2Ca 2Cu 3O x superconducting films of 1–80 μm thickness have been prepared on MgO(1 0 0) substrates using spraying process and post-Hg-vapor annealing. The effects of thickness on the grain alignment and J c properties have been investigated. The best T c and T zero were found to be 131.9 K and 129 K respectively, for 50 μm thick sample. Magnetic properties up to 6 T have been investigated. The calculated critical current density, J cmag, was found to be 4.8 × 10 5 A cm −2 at 4.2 K for 50 μm thick sample.

Response of thin-film SQUIDs to applied fields and vortex fields: Linear SQUIDs

In this paper we analyze the properties of a dc SQUID when the London penetration depth \lambda is larger than the superconducting film thickness d. We present equations that govern the static behavior for arbitrary values of \Lambda = \lambda^2/d relative to the linear dimensions of the SQUID. The SQUID's critical current I_c depends upon the effective flux \Phi, the magnetic flux through a contour surrounding the central hole plus a term proportional to the line integral of the current density around this contour. While it is well known that the SQUID inductance depends upon \Lambda, we show here that the focusing of magnetic flux from applied fields and vortex-generated fields into the central hole of the SQUID also depends upon \Lambda. We apply this formalism to the simplest case of a linear SQUID of width 2w, consisting of a coplanar pair of long superconducting strips of separation 2a, connected by two small Josephson junctions to a superconducting current-input lead at one end and by a superconducting lead at the other end. The central region of this SQUID shares many properties with a superconducting coplanar stripline. We calculate magnetic-field and current-density profiles, the inductance (including both geometric and kinetic inductances), magnetic moments, and the effective area as a function of \Lambda/w and a/w.

Microstructural and chemical analysis performed by HRTEM and EDS on YBa 2Cu 3O 7− x/Ag films irradiated with electrons

In this work, we have performed a high resolution transmission electron microscopy and chemical analyses by energy dispersive spectroscopy (EDS) on unirradiated and electron irradiated YBa 2Cu 3O 7− x /Ag superconductor thick films and found that due to the preparation method, the following phases could coexist: YBa 2Cu 3O (7− x) (YBCO), YBa 2Cu 4O 8 and YBa 2Cu 4O 10− x . These results could be corroborated by the HRTEM analyses performed in several areas of the material. The analysis reveal that the Ag added to the material, is located mainly at the interface between the YBCO crystals. One very important aspect of the electron-irradiated samples, with which the samples were subject, is the creation of many defects scattered randomly through out the material. These defects, mainly as bending planes promote stacking faults and are presumably responsible of the enhancement of the inter grain density current, as supporting results reported previously.

Fabrication and properties of (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting thick films

Approximately 50 µm thick epitaxial c-axis orientated (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting films have been prepared on MgO(100) substratesusing a spraying process and post-Hg-vapour annealing. The effects ofthe heating temperature–time combinations and the filling factor of Hg(ffHg) on the physical, electrical and magnetic properties of the thick films have been investigated.The interesting observation was the formation of a thick interfacial layer between the film and the substrates. This interfacial layerwas found to be protective against excessive diffusion and dissolution of theMg2+ ions from the substrate or counter-diffusion of Ba, Ca and Cuions from the films. The XRD investigations showed that thea–b plane of the HgRe-1223 phase aligns parallel to the substrate surface. The bestTc and Tzero were found to be 131.9 and 129.3 K, respectively. Magnetic properties up to5 T have been investigated. The calculated value of critical current density,Jc, wasfound to be 4.82 × 105 A cm−2 at 4.5 K. The results obtained suggested that fabrication of HgRe-1223 thick filmsuperconductors using a spraying process with 130 K transition is possible and they are verypromising particularly for electronic applications.

Field solutions for the Swihart wave and surface plasmon in superconducting/dielectric film multilayer structures in the mixed state

Microwave propagation characteristics in superconducting/dielectric multilayer structures in the mixed state are theoretically investigated. We use the electrodynamic field equations for a type-II superconductor in the mixed state to derive the field solutions for two model structures such as a superconducting planar waveguide and a superlattice. With these solutions, we present several quantitative studies of the propagation constant as a function of static magnetic field, superconducting film thickness, and radiation frequency for the Swihart wave, surface plasmon, and the dielectric image waveguide, respectively. In the waveguide structure, it is found that there exists a certain value of thickness of superconducting film such that the attenuation constant attains a minimum. This value is shown to increase with increasing static magnetic field. This behavior, however, is smeared out in the superconducting superlattice structure regardless of the applied static magnetic field. The roles played by the superconducting film thickness together with the vortices in the microwave propagation for a multilayer structure are thus elucidated.

Growth mechanism of Sm 2BaCuO 5 crystal fiber

During the growth of SmBa 2Cu 3O z superconductor thick film by a liquid phase epitaxy (LPE) process, some needle-like Sm 2BaCuO 5 crystal fibers were obtained. The long axis of the whiskers was in <001> direction, and the crystal faces appearing were (010), (110) and (210). Using Fourier-spectrum analysis, several characteristic peaks of [SmO 7] polyhedra were detected in the melt quenched from the growth temperature. The growth mechanism of Sm 2BaCuO 5 crystal fibers could be explained from the viewpoint of the formation of the growth unit and the incorporation of the growth unit into different interfaces. Assembling of growth units [SmO 7] into the (100) face has a comparatively strong bonding force, and the direction of this crystal face has a fast growth rate, thus the (100) face of the crystal disappears. The assembling of [SmO 7] into (010) and (110) faces has a relatively small bonding force, and those crystal faces have a smaller growth rate. The <001> screw axis of Sm-211 crystal promotes the growth of the <001> direction; therefore, the long axis of the fiber is in the <001> direction.

Magnetic imaging of pearl vortices in artificially layered (Ba0.9Nd0.1CuO2+x)m/(CaCuO2)n systems.

We have used scanning SQUID magnetometry to image vortices in ultrathin (Ba0.9Nd0.1CuO2+x)(m)/(CaCuO2)(n) high temperature superconductor samples, with as few as three superconducting CuO2 planes. The Pearl lengths (Lambda=2lambda(2)(L)/d, lambda(L) the London penetration depth, d the superconducting film thickness) in these samples, as determined by fits to the vortex images, agree with those by local susceptibility measurements, and can be as long as 1 mm. The in-plane penetration depths lambda(ab) inferred from the Pearl lengths are longer than many bulk cuprates with comparable critical temperatures. We speculate on the causes of the long penetration depths, and on the possibility of exploiting the unique properties of these superconductors for basic experiments.

THz imaging of supercurrent distribution in Meissner state of LPE-BSCCO film

In order to apply the terahertz (THz) imaging technique to high-TC superconductor thick film, the THz imaging system was improved to observe the back-scattered THz radiation pulse. Using the improved system we succeeded in the observation of supercurrent distribution in Bi2Sr2CaCu2O8+δ thick film in Meissner state.