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.
Size effect on variable-range-hopping transport in PrBa2Cu3O7-x.
Normal transport properties and their size effect of PrBa 2 Cu 3 O 7-x are studied using planar-type junction specimens. The transport properties of PrBa 2 Cu 3 O 7-x are in accordance with a variable-range-hopping mechanism. The localized wave function for this conduction has a decay length of 8.5 nm, and the hopping distance is 96 nm at 2 K. The conductance properties of junctions with a length of a few times the hopping distance show a size erect. A Coulomb correlation gap is observed at temperatures lower than 4 K, and the minimum conductance at the Coulomb gap depends weakly on temperature and magnetic field
Magnetic ordering in (Y1-xPrx)Ba2Cu3O7 as evidenced by muon spin relaxation
Using the zero‐field‐muon‐spin‐relaxation (μSR) technique clear evidence has been found for antiferromagnetic ordering of Cu moments within the CuO planes of (Y1−xPrx)Ba2Cu3O7. The Neel temperatures are approximately 285, 220, 35, 30, and 20 K for x=1, 0.8, 0.6, 0.58, and 0.54, respectively. For x=0.50 we observe a fast‐relaxing component of the muon polarization in addition to a long‐time tail, reminiscent of spin‐glass behavior. This region of the phase diagram (0.5≤x≤0.54) corresponds to the existence of both superconductivity and magnetism. The fully developed local magnetic field for x>0.54 is found to be ∼16 mT, but decreases to ∼12 mT at T=17 K for the x=1 sample, presumably due to the onset of Pr‐ion ordering. Magnetic ordering also occurs in PrBa2Cu3O6; the Neel temperature is ∼325 K.