Enhancement of flux pinning and critical currents in YBa 2 Cu 3 O 7 − δ films by nanoscale iridium pretreatment of substrate surfacesThis paper shows that the combination of self-assembled structures in the form of "whiskers" and nanoparticles, which appear as a result of the joint sintering powders YBa 2 Cu 3 O 7Àx and arc nanopowders CuO, leads to a significant increase in the current density and the appearance of the peak effect in strong magnetic fields range. Very high critical current density appears from a complex vortex pinning, where the defects in the form of "whiskers" provides more energy of pinning, and nanoparticles inhibit the flux creep. Regulation of the morphology of such structures can be achieved by simple change of the concentration of nanodispersed additives. It is shown that the optimal additive is CuO equal to 20 wt. %. V C 2015 AIP Publishing LLC.

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Copper oxide nanoparticles were produced by direct plasmachemical synthesis in a plasma arc discharge of low pressure. The formation of CuO nanoparticles with an average size of 12 nm and narrow size distribution intervals was determined by using the X-ray diffraction analysis and TEM microscopy methods. It was defined by using a vibration magnetometer and a SQUID magnetometer, that the magnetic properties of CuO nanoparticles with such size were extremely different from the magnetic properties of bulk antiferromagnetic CuO. Structural defects, caused the formation of a ferromagnetic state, remaining at least up to the room temperature. The temperature of corresponding antiferromagnetic ordering was significantly decreased (down to ~ 100 K). Meanwhile, some of the copper surface spins showed a spin-glass behavior at low temperatures.