We report first–principles frozen–phonon calculations for the determination of the force–free geometry and the dynamical matrix of the five Raman–active A1g modes in YBa2Cu3O7. To establish the shape of the phonon potentials atomic forces are calculated within the LAPWmethod. Two different schemes – the local density approximation (LDA) and a generalized gradient approximation (GGA) – are emplo...

Abstract Two different types of monoclinic HfO 2 nanocrystals were employed in this work to study the effect nanocrystal shape and crystallinity on structural defects YBa2Cu3O7−δ (YBCO) matrix as it leads an enhancement pinning performances solution-derived YBCO nanocomposite films. In nanorod-like obtained from surfactant-controlled synthesis led short intergrowths surrounding particles, while...

– We have studied the dynamics of magnetic-flux avalanches in superconducting YBa2Cu3O7−δ films by means of a fast magneto-optic pump-probe technique. Two regimes of propagation are found: in regime I, directly after the nucleation of the avalanches by a femtosecond laser pulse, the velocity v of the flux dendrites depends strongly on the magnetic field, and values of v up to 180 km/s are obser...

The planar oxygen isotope effect coefficient measured as a function of hole doping in the Prand La-doped YBa2Cu3O7 (YBCO) and the Ni-doped La1.85Sr0.15CuO4 (LSCO) superconductors quantitatively and qualitatively follows the form originally proposed by Kresin andWolf [Phys. Rev. B 49, 3652 (1994)], which was derived for polarons perpendicular to the superconducting planes. Interestingly, the inv...