Effective Magnetic Field Dependence of the Flux Pinning Energy in FeSe0.5Te0.5 Superconductor

The role of a layered structure in superconducting pinning properties is still at a debate. The effects of the vortex shape, which can assume for example a staircase form, could influence the interplay with extrinsic pinning coming from the specific defects of the material, thus inducing an effective magnetic field dependence. To enlighten this role, we analysed the angular dependence of flux pinning energy U(H,θ) as a function of magnetic field in FeSe0.5Te0.5 thin film by considering the field components along the ab-plane of the crystal structure and the c-axis direction. U(H,θ) has been evaluated from magneto-resistivity measurements acquired at different orientations between the applied field up to 16 T and FeSe0.5Te0.5 thin films grown on a CaF2 substrate. We observed that the U(H,θ) shows an anisotropic trend as a function of both the intensity and the direction of the applied field. Such a behaviour can be correlated to the presence of extended defects elongated in the ab-planes, thus mimicking a layered superconductor, as we observed in the microstructure of the compound. The comparison of FeSe0.5Te0.5 with other superconducting materials provides a more general understanding on the flux pinning energy in layered superconductors.

Difference in anisotropic vortex pinning in pristine and proton-irradiated (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 single crystals

To study the difference in the vortex pinning mechanism between in-plane and out-of-plane and the change of these pinning mechanisms due to defects induced by proton irradiation, the in-plane electrical resistivity for pristine and proton irradiated (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 single crystals in B//c and B//ab up to B = 13 T. Both samples showed a monoclinic crystal structure, which was different from previously known, through crystal structure analysis using the selected area electron diffraction (SAED) method. The protons irradiation incident along the c-axis caused expansion of the lattice constants a and b. The electronic structure changed by the expansion of this lattice constant affected the change of the coherence length ξc significantly shorter than the distance between the superconducting Fe2As2 layers. The vortex in B//ab was mainly pinned by the newly formed normal component with zero Cooper pair due to the short ξc, and ξc increased by proton irradiation reduced the pinning energy. On the other hand, the vortex in B//c was mainly pinned by point defects, and the point defects increased by proton irradiation increased the pinning energy.

Dynamics of splashed droplets impacting wheat leaves treated with a fungicide

Wheat is threatened by diseases such as leaf rust. One significant mechanism of disease spread is the liberation and dispersal of rust spores due to rainsplash. However, it is unclear to what extent the spore-laden splashed droplets can transmit the disease to neighbouring leaves. Here, we show that splashed droplets either bounce or stick, depending on the orientation of the leaf and whether the surface of the leaf has been treated with a fungicide. A scaling model revealed that bouncing was enabled when the droplet’s kinetic energy exceeded its pinning energy to the surface. Our findings indicate that, ironically, the application of fungicide to protect a wheat plant may also facilitate pathogen spread and infection by making leaves sticky to spore-laden droplets.

Magnetic relaxation in (Bi, Pb)-2223 superconducting ceramics doped with α-Al2O3 nanoparticles

A preliminary study of the magnetic relaxation in (Bi, Pb)-2223 superconducting ceramics doped with α-Al2O3 nanoparticles is presented, taking as starting point the measurements of the M(t) dependence, both in samples in the form of powder as in pellet. The relaxation of the three types of vortices that can exist inside these materials is analyzed, emphasizing on the intragranular regionwhere the planar defects exist and, consequently, Abrikosov-Josephson vortices emerge. Finally, interesting results of the comparison between the behavior of the samples in the form of powder and in the form of pellet are shown from the estimation of the pinning energy of the vortices.