A non-destructive evaluation (NDE) system was set up in our laboratory. A high-Tc dc superconducting quantum interference device (dc SQUID) made from YBa2Cu3O7−δ thin film on a 24◦ bicrystal SrTiO3 substrate was adopted as the magnetic flux sensor. Novel excitation coils and a balance circuitry were proposed and employed for evaluation of multilayer aluminium structure with artificial slits in ...

In-plane resistance and magnetization measurements were performed on La0:7Ca0:3MnO3=YBa2Cu3O7 d=La0:7Ca0:3MnO3 (LCMO/ YBCO/LCMO) trilayers below the superconducting transition temperature of the YBCO layer. Two magnetoresistance (MR) peaks were found: The first MR peak is consistent with the suppression of superconductivity due to the stray fields generated by the domain walls and the second on...

We report on three different and complementary measurements, namely magnetisation measurements positron annihilation spectroscopy and NMR measurements, which give evidence that the formation of oxygen vacancy clusters is on the origin of the fishtail anomaly in YBa2Cu3O7−δ. While in the case of YBa2Cu3O7.0 the anomaly is intrinsically absent, it can be suppressed in the optimally doped state wh...

Recent magnetic measurements at La0.67Ca0.33MnO3/YBa2Cu3O7 interfaces led to conflicting interpretations: a magnetic "dead" layer on the LCMO side or antiparallel Cu and Mn magnetic moments. Here we report results of first-principles density-functional calculations of position-dependent magnetic couplings between interlayer and intralayer Mn atoms. The couplings in the first few layers near the...

We use the experimental technique of thermal modulation reflectometry to study the relatively small temperature dependence of the optical conductivity of superconductors. Due to a large cancellation of systematic errors, this technique is shown to a be very sensitive probe of small changes in reflectivity. We analyze thermal modulation reflection spectra of single crystals and epitaxially grown...

We report on marked memory effects in the vortex system of twinned YBa2Cu3O7 single crystals observed in ac susceptibility measurements. We show that the vortex system can be trapped in different metastable states with variable degree of order arising in response to different system histories. The pressure exerted by the oscillating ac field assists the vortex system in ordering, locally reduci...

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...