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We probe the short-range pinning properties with the application of microwave currents at very high driving frequencies (47.7 GHz) on YBa$_2$Cu$_3$O$_{7-delta}$ films with and without sub-micrometer BaZrO$_3$ inclusions. We explore the temperature and field ranges 60 K$<T<T_c$ and 0$<mu_0H<$0.8 T, with the field applied along the c-axis. The magnetic field induces a much smaller increase of the microwave resistivity, $Delta rho_1(H)+mathrm{i}Delta rho_2(H)$, in YBa$_2$Cu$_3$O$_{7-delta}$/BaZrO$_3$ with respect to pure YBa$_2$Cu$_3$O$_{7-delta}$. $Delta rho_1(H)$ is slightly superlinear in pure YBa$_2$Cu$_3$O$_{7-delta}$ (suggesting a possible contribution of thermal activation), but linear or sublinear in YBa$_2$Cu$_3$O$_{7-delta}$/BaZrO$_3$ (suggesting a possible suppression of thermal activation as a consequence of BaZrO$_3$ inclusions). These features persist up to close to $T_c$. We discuss our data in terms of the ratio $r=Delta X_s(H)/Delta R_s(H)$ in the framework of the models for the microwave surface impedance in the mixed state. Large $r$ are found in YBa$_2$Cu$_3$O$_{7-delta}$/BaZrO$_3$, with little field dependence. By contrast, smaller values and stronger field dependences are found in pure YBa$_2$Cu$_3$O$_{7-delta}$. We discuss the different field dependence of the pinning constant.
We present measurements of the magnetic field dependent microwave surface resistance in laser-ablated YBa$_2$Cu$_3$O$_{7-delta}$ films on SrTiO$_3$ substrates. BaZrO$_3$ crystallites were included in the films using composite targets containing BaZrO
In order to study the vortex pinning determined by artificially introduced pinning centers in the small-vortex displacement regime, we measured the microwave surface impedance at 47.7 GHz in the mixed state of YBa$_{2}$Cu$_{3}$O$_{7-delta}$ thin film
We report on the field dependence of the microwave complex resistivity data in YBa$_2$Cu$_3$O$_{7-x}$/BaZrO$_3$ films grown by PLD at various BaZrO$_3$ content. The data, analyzed within a recently developed general framework for the mixed-state micr
Superconductors can support large dissipation-free electrical currents only if vortex lines are effectively immobilized by material defects. Macroscopic critical currents depend on elemental interactions of vortices with individual pinning centers. P
We discuss pinning properties of MgB2 thin films grown by pulsed-laser deposition (PLD) and by electron-beam (EB) evaporation. Two mechanisms are identified that contribute most effectively to the pinning of vortices in randomly oriented films. The E