Growth and superconducting transition of epitaxial thin films
thin films have been grown on SrTiO3 (STO) and yttrium-stabilized ZrO2 (YSZ) substrates by pulsed laser ablation. The substrate temperature dependence of orientation and superconducting properties were systematically studied. Good quality c-axis and a-axis orientated films can be obtained on SrTiO3 solely by changing the substrate temperature. On YSZ, films with good c-axis orientation can be grown, while it is hard to grow films with good a-axis orientation by changing substrate temperature alone. The highest TC 0 is about 37 K, which is found in the films grown on YSZ with a good c-axis orientation. For the films grown on STO, however, the highest TC 0 is about 35.6 K, with a mixed orientation of c-axis and a-axis. In most of the superconducting films, the weak temperature dependence of the normal state resistivity, as characterized by small ratios, together with a weak localization behaviour just above TC, could be attributed to the essential scattering due to the localized electronic states. The superconducting transitions in a field up to 10 T along the c-axis have been measured on a c-axis oriented film grown on SrTiO3. The zero-temperature in-plane upper critical field BC 2ab(0) is estimated from the resistivity transition data.
Neutron and X-ray scattering studies of magnetism in non-superconducting PrBa2Cu3O6+x
Abstract I give a short review of neutron and X-ray scattering experiments undertaken to study the magnetic properties of non-superconducting PrBa 2 Cu 3 O 6+ x . The measurements have confirmed the magnetic ordering of the Pr sublattice at temperatures below T Pr ≈20 K, and have revealed an incommensurate magnetic structure with a long period (∼600 A) involving both the Pr and Cu spins. The Cu spins in this Pr ordered phase are found to be non-collinear. Taken as a whole, the results provide strong evidence for a substantial magnetic coupling of the pseudodipolar type between the Pr and Cu ions. The effect of this coupling is also evident in the spectrum of low energy magnetic excitations determined by neutron inelastic scattering.
Thermodynamic and pressure dependent magnetic characteristics of PrBa2Cu3O7
Abstract The temperature dependence of the specific heat and magnetic susceptibility of PrBa 2 Cu 3 O 7 indicates that it is nonsuperconducting for T > 1.0 K but magnetically orders in the vicinity of 17 K. The entropy removal associated with this magnetic transition is 5 J/mol K and the isothermal magnetization at T = 4.2 K to 23 T shows no evidence of saturation.