Angle dependent molecular dynamics simulation of flux pinning in YBCO superconductors with artificial pinning sites

A molecular dynamics (MD) simulation to simulate the vortices in superconductors with artificial pinning sites is presented. The simulation reproduces the correct anisotropic behavior in angular dependence of critical current. We also show that the shape of the J(c)(B) curve depends on the size of the pinning sites and the change from p = 0.5 to p approximate to 1 is due to the breaking of the vortex lattice to individually acting vortices. The results beautifully correspond to experimental data. Furthermore, we found that the size and shape of the c-axis peak observed with columnar pinning sites in J(c)(theta) also depends on the size of the rods, larger pinning sites leading to wider peaks. The results obtained from the MD-simulation are similar to those of the much more computationally intensive Ginzburg-Landau simulations. Furthermore, the MD-simulations can provide insight to the vortex dynamics within the samples

The Angular Dependence of the Critical Current of BaCeO3 Doped YBa2Cu3O6+x Thin Films

The angular dependencies of the critical current of BaCeO3 (BCO) doped YBa2Cu3O6+x (YBCO) thin films grown with pulsed laser deposition (PLD) on SrTiO3 (001) were systematically investigated. The BCO concentration in the YBCO matrix was varied between 0-8 wt.%. Transmission electron microscopy confirmed that the 4% BCO containing sample has point-like, partly agglomerated BCO particles with diameter of 2.5 nm. The dopant degrades the crystal quality of YBCO but improves its in-field current carrying performance especially at low temperatures. The BCO addition affects the angular dependence of the critical current by broadening the B parallel to ab-axis peak of YCBO but no c-axis peak is seen, which is contrary to BaZrO3 doped films made by PLD. Although the particles are point-like, it is found that a model featuring only isotropic pinning centers is not sufficient to describe the angular dependence of the samples where B parallel to ab-axis of YCBO.</p

Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods

The flux pinning properties of the high temperature superconductor YBa2Cu3O7-d (YBCO) have been conventionally improved by creating both columnar and dot-like pinning centres into the YBCO matrix. To study the effects of differently doped multilayer structures on pinning, several samples consisting of a multiple number of individually BaZrO3 (BZO) and BaCeO3 (BCO) doped YBCO layers were fabricated. In the YBCO matrix, BZO forms columnar and BCO dot-like defects. The multilayer structure improves pinning capability throughout the whole angular range, giving rise to a high critical current density, J(c). However, the BZO doped monolayer reference still has the most isotropic J(c). Even though BZO forms nanorods, in this work the samples with multiple thin layers do not exhibit a c axis peak in the angular dependence of J(c). The angular dependencies and the approximately correct magnitude of J(c) were also verified using a molecular dynamics simulation

The effect of BaCeO3 dopant concentration on magnetically defined B-irr and B-c2 in YBa2Cu3O6+x, thin films deposited on SrTiO3 substrates

The effect of BaCeO3 (BCO) dopant concentration on magnetically obtained irreversibility field B-irr and upper critical field B-c2 is investigated in YBa2Cu3O6+x (YBCO) thin films prepared by pulsed laser deposition on SrTiO3 (001) substrates. The unchanged values of B-irr and B-c2 are connected to the structural properties where BCO has been observed to form non-elongated and randomly distributed particles within the whole concentration range of 0 - 10 wt.%. This indicates a different type of flux pinning mechanism for BCO-doped YBCO than for the widely studied BaZrO3-doped YBCO where increased B-irr and B-c2 values were observed

Dirty limit scattering behind the decreased anisotropy of doped YBa2Cu3O7-delta thin films

We measured the resistivity of pulsed-laser-deposited BaCeO3 (BCO)-doped YBCO thin films containing spherical BCO particles in fields up to 30 T. The average diameter of the particles depends on the dopant concentration being below 4 nm in all the samples. Raised values of the upper critical field, B-c2, were observed in all the samples. Additionally, the parameter gamma, describing the electron mass anisotropy, decreased from 6.2 in the undoped sample to 3.1 in the 8 wt.% BCO-doped sample. These results can be explained by the increased number of defects decreasing the mean free path of electrons and thus lowering the coherence length, which in turn increases B-c2

Heteronuclear nanoparticles supported hydrotalcites containing Ni(II) and Fe(III) stable photocatalysts for Orange II degradation

Hydrotalcites containing Ni(II) and Fe(III) was synthesized using co-precipitation method to demonstrate their use as a support material for the homogeneous deposition of Au and Au-Pd nanoparticles via solimmobilization. Detailed characterization performed by UV–Vis, ATR-FTIR, TGA, Mössbauer spectroscopy, SEM,Cryo-TEM, BET analysis evidenced the structural, morphological and textural properties of the passive support and decoration of nanoparticles on the surface of LDH and evidenced the property to be used as photocatalysts. Thesematerials proved to be efficient photocatalysts for the degradation of environmentally important Orange II dye (OII) as amodel pollutant. Different experimental parameters influencing the photocatalytic activity viz., catalyst dosage, initial dye concentration and reusability of the catalystwere studied. Langmuir-Hinshelwood model was used to analyze the kinetics of the photocatalytic process. Heteronuclear Au-Pd nanoparticles immobilized on NiFeCO3 LDH was found to be the best photocatalyst degrading about 95% of the dye (25 mg/L) after 60 min and this activity remains to be nearly the same after recycling the catalyst. This enhancement in the activity was attributed to the presence of Au-Pd Nps, with specific surface area (80 m2/g), and band gap (2.7 eV). Our study shows the prepared photocatalyst anticipates being a promising candidate for other photocatalytic applications

Angular and field dependent flux pinning in artificially doped YBCO films on IBAD-MgO based template

The self-organized artificial pinning structure in superconducting thin films of YBa2Cu3O6+x (YBCO) is optimized on a new type of IBAD-MgO based template by doping YBCO with non-superconducting BaCeO3 (BCO) and BaZrO3 (BZO). In these films, the YBCO is well ordered, no large angle grain boundaries are seen and the isotropic BCO particles are randomly distributed while the BZO grows as unidirectionally splayed and shortened nanorods. Additionally, the low-angle grain boundaries formed during the growth process have an impact on the flux pinning. The flux pinning behaviour can be explained by the vortex path model, where the pinning paths are shorter in BZO doped than in BCO doped films. In BZO doped films, the vortices are pinned with greater pinning force and thus the critical current density J(c) is higher than in BCO doped films, especially in high magnetic fields, where the wide peaks in J(c)(theta) were seen along the YBCO c-direction. This direction dependent pinning can be explained by the nearly similar diameters of BZO nanorods with those of vortices, thus efficiently increasing the vortex pinning in the vicinity of YBCO c-axis

Angular and field dependent flux pinning in artificially doped YBCO films on IBAD-MgO based template

The self-organized artificial pinning structure in superconducting thin films of YBa2Cu3O6+x (YBCO) is optimized on a new type of IBAD-MgO based template by doping YBCO with non-superconducting BaCeO3 (BCO) and BaZrO3 (BZO). In these films, the YBCO is well ordered, no large angle grain boundaries are seen and the isotropic BCO particles are randomly distributed while the BZO grows as unidirectionally splayed and shortened nanorods. Additionally, the low-angle grain boundaries formed during the growth process have an impact on the flux pinning. The flux pinning behaviour can be explained by the vortex path model, where the pinning paths are shorter in BZO doped than in BCO doped films. In BZO doped films, the vortices are pinned with greater pinning force and thus the critical current density J(c) is higher than in BCO doped films, especially in high magnetic fields, where the wide peaks in J(c)(theta) were seen along the YBCO c-direction. This direction dependent pinning can be explained by the nearly similar diameters of BZO nanorods with those of vortices, thus efficiently increasing the vortex pinning in the vicinity of YBCO c-axis

The Angular Dependence of the Critical Current of BaCeO3 Doped YBa2Cu3O6+x Thin Films

The angular dependencies of the critical current of BaCeO3 (BCO) doped YBa2Cu3O6+x (YBCO) thin films grown with pulsed laser deposition (PLD) on SrTiO3 (001) were systematically investigated. The BCO concentration in the YBCO matrix was varied between 0-8 wt.%. Transmission electron microscopy confirmed that the 4% BCO containing sample has point-like, partly agglomerated BCO particles with diameter of 2.5 nm. The dopant degrades the crystal quality of YBCO but improves its in-field current carrying performance especially at low temperatures. The BCO addition affects the angular dependence of the critical current by broadening the B parallel to ab-axis peak of YCBO but no c-axis peak is seen, which is contrary to BaZrO3 doped films made by PLD. Although the particles are point-like, it is found that a model featuring only isotropic pinning centers is not sufficient to describe the angular dependence of the samples where B parallel to ab-axis of YCBO