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YBaCuO (YBCO) thin films have been deposited on bare and LaSrMnO (LSMO) modified single crystal SrTiO (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field. [ABSTRACT FROM AUTHOR]

Thin films of YBCO and YBCO:BaZrO (BZO) nanocomposite have been deposited using the pulsed laser deposition technique. Substantial increase in critical current density ( J) and pinning force density ( F) of the nanocomposite thin films was observed. The possible pinning mechanism in YBCO:BZO nanocomposite thin films has been explored and compared with the pinning mechanism in pure YBCO thin film by studying the variation of J with magnetic field ( B) and temperature. In the intermediate field regime (0.1-1 T), J follows B with nearly similar values of α for YBCO and YBCO:BZO nanocomposite thin films indicating similar pinning mechanism in both thin films. The variation of J with reduced temperature ( t= T/ T) has been studied for both the films and it was observed that the mechanism of pinning in both YBCO and YBCO:BZO thin films is similar ( δT pinning). The observed enhanced values of J and F of the nanocomposite thin film is attributed to the presence of BZO nanoparticles, which induces more defects due to lattice mismatch between YBCO and BZO leading to improved flux pinning properties of the nanocomposite thin film. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of YBa2Cu3O7− δ (YBCO) have been deposited on undecorated and La0.67Sr0.33MnO3 (LSMO) nanoparticles decorated single crystal SrTiO3 (STO) substrate using laser ablation technique and their flux pinning characteristics have been compared using temperature dependent magnetization studies. Significant improvement in the critical current density of YBCO thin film has been observed even at higher applied magnetic field (∼7T). The improved flux pinning properties of YBCO thin films deposited on LSMO decorated STO substrate has been attributed to the presence of ferromagnetic LSMO nanoparticles at the substrate/film interface which seem to be acting as artificially generated magnetic pinning centres leading to improved flux pinning properties. [Copyright &y& Elsevier]

Abstract: The effect of incorporation of BaTiO3(BTO) nanoparticles on the flux pinning properties of pulsed laser deposited YBCO:BTO thin films was studied. Substantial increase in the critical current density () and the pinning force density () of the nanocomposite thin films was observed. At 77 K, and zero applied magnetic field, the value of for YBCO and YBCO:BTO (2%) thin films were 2.93 MA/cm2 and 6.43 MA/cm2, respectively. At the same temperature and an applied magnetic field of 4 T, the value of increases from 3.6×104 A/cm2 for YBCO thin film to 2.7×105 A/cm2 for YBCO:BTO (2%) nanocomposite thin film. The study of temperature and field dependence of of YBCO and YBCO:BTO thin films indicates similar type of pinning. The lattice mismatch between YBCO and BTO seems to introduce more defects resulting in the improvement of flux pinning properties. [Copyright &y& Elsevier]

Abstract: Magnetization studies of YBCO:BaZrO3 composite superconductor have been done over a wide range of temperature and applied magnetic field using MPMS SQUID VSM and the results are compared with that of pure YBCO. The analysis of the observed results indicate that there is considerable improvement in the values of critical current density (J C ) and pinning force density (F p ) of YBCO:BaZrO3 composite samples as compared to pure YBCO sample in the entire investigated range of applied magnetic field and temperatures ranging from 4 to 77K. The variation of J C with reduced temperature t (=T/T C ) for the composite samples has been found to be similar to that of pure YBCO sample indicating similar nature of the vortex interaction with pinning centres in both pure and composite samples. The enhancement in the value of J C and F p in the composite samples as compared to pure YBCO sample has been attributed to the increased defect density in the composite samples due to the presence of BZO particles in YBCO matrix. [Copyright &y& Elsevier]

In the present work, the effect of the addition of potassium niobate (KNbO3) nanoparticles (NPs) on the pinning properties of YBCO compound is investigated. The synthesis of YBCO:xKNbO3 (x = 0–1 wt%) nanocomposites were carried out using a two-step process, firstly KNbO3 NPs were synthesized via hydrothermal process, and later on, the nanocomposites were synthesized via solid-state reaction method containing various concentrations of NPs from 0 to 1 wt%. The effect of NPs of KNbO3 in YBCO is studied using structural, morphological, transport, and magnetic measurements. From XRD spectra, the crystal structure of YBCO was found to be orthorhombic, which remained invariant even in the nanocomposites. Magnetic properties of YBCO and its nanocomposites over the range of − 6 T to + 6 T were characterized using magnetic property measurement system (MPMS). The Bean model is applied to calculate the critical current density (JC), which has improved in YBCO:KNbO3 nanocomposites as compared to YBCO. The maximum enhancement of ~ 4.4 times in JC and pinning properties was found for YBCO:0.5wt%KNbO3 nanocomposites due to the creation of defects in YBCO matrix. Additionally, it is observed that for nanocomposites compared to YBCO, the rate of JC decay decreases with an increase of externally applied field, which indicates an enhancement in pinning properties of nanocomposites. [ABSTRACT FROM AUTHOR]

Introduction of artificial pinning centres in different morphology is a beneficial way to improve the flux pinning properties of a YBCO compound. In the present study, we report the effect of addition of sodium niobate (NaNbO 3) nanostructures in two different form i.e. nanorods (NRs) and nanoparticles (NPs) with a varied wt% (0, 0.5, and 1 wt%) on the pinning capabilities of bulk YBCO polycrystalline samples. The orthorhombic crystal structure of YBCO was confirmed by the XRD spectra even in the nanocomposite samples. The existence of NPs or NRs on the surface and between the superconducting grains of YBCO was confirmed by morphological analysis. The critical temperature (T c) remains almost unchanged as compared to pure YBCO on addition of NaNbO 3 nanostructure in YBCO compound upto 1 wt% concentration. Even at higher fields (upto 6 T) and higher temperatures (upto 75 K), the addition of NaNbO 3 NPs or NRs in YBCO nanocomposite resulted in a significant increase of ~2.6 times in the critical current density as compared to pure YBCO. In comparison to NRs added YBCO nanocomposite samples, NPs added YBCO nanocomposite samples showed higher improvement. Throughout the entire investigated range of applied field, the maximum pinning force was found for 0.5 wt% NPs added composite sample. [ABSTRACT FROM AUTHOR]

In the present work, we are reporting the impact of addition of sodium niobate (NaNbO3) nanoparticles (NPs) on the flux pinning properties of YBCO compound with different wt% (0 to 2%) of NaNbO3. The structural analysis reveals that the orthorhombic crystal structure of YBCO remains unchanged in the nanocomposite samples. The presence of NaNbO3 in the YBCO nanocomposites is confirmed by elemental analysis technique. No significant change in the superconducting transition temperature is observed on addition of NaNbO3 NPs in YBCO compound for up to 2 wt% concentration. Magnetization hysteresis loop measurement indicates a significant enhancement in the value of critical current (JC) and pinning force (FP) in the YBCO/x NaNbO3 (NP) composite samples which is attributed to the generation of sufficient no. of defect centers in YBCO matrix due to addition of NPs of NaNbO3. At lower fields and temperature range 10–60 K, the 0.5 wt% NP-added composite sample has shown maximum enhancement in JC whereas at higher temperatures and higher fields, the maximum improvement in the pinning properties is observed for 0.25 wt% NaNbO3-added YBCO sample. [ABSTRACT FROM AUTHOR]

In this study, the effect of addition of nanostructures of Sodium niobate (NaNbO 3) having different morphology i.e. Nanoparticles (NPs) or Nanorods (NRs) on the magneto-transport properties of Y 1 Ba 2 Cu 3 O 7-δ -NaNbO 3 nanocomposite are investigated. NaNbO 3 nanostructures are synthesized by hydrothermal technique whereas Pristine and NaNbO 3 added Y 1 Ba 2 Cu 3 O 7-δ (YBCO) samples are synthesized through Solid state reaction route. Superconducting transition in electrical measurement showed increased broadening with the increase in applied magnetic field. This broadening is smaller in YBCO composite samples than pristine YBCO indicating better coupling among superconducting grains in the nanocomposites. The tailing effect in the superconducting transition temperature is due to the flux flow of vortices. Further, the activation energy (Uₒ) estimated from ln(ρ) vs 1/T variation indicated its increased value in the nanocomposite YBCO showing enhanced flux pinning. From the applied magnetic field dependence of Uₒ for pristine YBCO and nanocomposite samples, the presence of planar and point defects was confirmed depending on the applied field value. The upper critical field (H C 2 (0)) estimated using Ginzburg-Landau (GL) theory indicated enhancement in H C 2 (0) for the nanocomposite samples, with larger enhancement in NPs added YBCO as compared NRs added YBCO. For 0.5 wt% NaNbO 3 NPs added YBCO samples, the highest enhancement of H C 2 (0) (∼1.2 times) as compared to YBCO and other composite samples was achieved whereas further increase of concentration of NPs or NRs in YBCO compound leads to decrement in H C 2 (0) which is due to increased agglomeration between superconducting grains. [ABSTRACT FROM AUTHOR]

• No change in the orthorhombic crystal structure of YBCO in all nanocomposite samples. • A decrease in T c from 92 K to 90.5 K for 2 wt% concentration of NaNbO 3 in nanocomposite sample. • Significant enhancement in critical current density and pinning force of the order of ~2.5 times for 0.5 wt% added composite sample in comparison to pure YBCO. In this work, sodium niobate (NaNbO 3) nanorods (NR) – YBCO superconductor composites with different wt% (0–2%) of NaNbO 3 were prepared via a two-step process of hydrothermal and solid-state reaction, and its structural, electrical, and magnetic characterizations were carried out. XRD studies revealed that the orthorhombicity of YBCO is preserved in all nanocomposite samples. The superconducting transition temperature decreases from 92 K to 90.5 K when the addition of NaNbO 3 was increased to 2 wt%. Magnetization studies revealed a significant increase of critical current (J c) and pinning force (F p) in the NaNbO 3 (NR) added YBCO sample which has been attributed to the creation of artificial pinning centers due to the presence of NaNbO 3 NR. For the 0.5 wt% nanorods added sample, the enhancement in J c and F p was maximum. Temperature and field dependence of J c were carried out to probe the nature of pinning in the nanocomposite superconductors. [ABSTRACT FROM AUTHOR]