Study of magnetic flux pinning in granular YBa2Cu3O7 − y /nanoZrO2 composites

2017

J Supercond Nov Magn

Self Cite

Copper oxide nanoparticles, produced by direct plasmochemical synthesis in a lowpressure arc discharge plasma, show a wide variety of magnetic properties depending on the strength of the external magnetic field and the temperature. At low strength of the field and throughout the studied temperature range the ferromagnetic state dominates. This state is caused by disordering of the spins on the surface of the nanoparticles. At high strength of the field and under the temperatures of less than 200 K, nanoparticles exhibit a paramagnetic state due to the spin-glass behavior of copper atoms. At high strength of the field (more than 3 kOe) and under the temperature of above 300 K, the diamagnetic state of nanoparticles is observed, due to local eddy currents caused by oxygen vacancies. The temperature of antiferromagnetic ordering under study is significantly lowered (down to ~ 100 K).

Section: Introductionmentioning

confidence: 99%

Peculiarities of Magnetic Behavior of CuO Nanoparticles Produced by Plasma-Arc Synthesis in a Wide Temperature Range

Ушаков

2017

J Supercond Nov Magn

Self Cite

“…They lead to a distortion of the crystal structure at the interface and influence the distribution of oxygen-deficient areas, as well as to increasing the number of microareas with a low J c . 10 However, further increase in the magnetic field leads to sufficiently abrupt decrease of a current density down to 0. In this range of magnetic field, the dissipation occurs according to the Arrhenius law R % exp (ÀU(H)/T), 11 which is characteristic for the magnetic flux creep model with temperature-independent energy pinning U(H).…”

Section: Methodsmentioning

confidence: 99%

“…The features of the pinning in YBa 2 Cu 3 O 7Àx nanocomposite films, obtained by the dissolution method and containing randomly oriented non-superconducting "nanodots" BaZrO 3 , Y 2 O 3 , BaCeO 3 , and Ba 2 YTaO 6 with an average radius of (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) nm, are studied in the work. 2 The record pinning force of more than 20 GN/m 3 has been achieved in films with BaZrO 3 content about 10 mol.…”

Section: Introductionmentioning

confidence: 99%

Enhancing of magnetic flux pinning in YBa2Cu3O7−x/CuO granular composites

Ушаков

Journal of Applied Physics

et al. 2015

Self Cite

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.

“…The experimental equipment and the dependence of the powder properties on the spraying conditions are discussed. [9][10][11][12] The cathode consists of copper alloy M1 with diameter of 80 mm and length of 100 mm; it was placed on a water-cooled copper current lead. An auxiliary electrode was used to start the pilot arc, as it provided the plasma stream stabilization.…”

Section: Methodsmentioning

confidence: 99%

The influence of oxygen concentration on the formation of CuO and Cu2O crystalline phases during the synthesis in the plasma of low pressure arc discharge

Uschakov

et al. 2016

Vacuum

Abstract. This paper describes the synthesis of copper oxide nanoparticles with different percentages of CuO and Cu 2 O phases. It was achieved by the control of the percentage of oxygen in the gas mixture (N 2 + O 2 ) in a plasma-chemical process of evaporation-condensation by means of low-pressure arc discharge. In all the experiments, the pressure in the plasma-chemical reactor remained constant at 60 Pa. By means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) it was found that the average particle size was 6 nm, and Cu 2 O phase content decreases with increasing oxygen content in the gas mixture. High photocatalytic properties of Cu 2 O powder were shown by the example of the reaction of the methyl orange dye decomposition in water solution. The problems, associated with the performance of this method and the formation of crystalline phases, are discussed.