a-axis oriented epitaxial YBa2Cu3O7−y/PrBa2Cu3−xNbxO7−z multistructures

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Abstract
Using the pulsed laser deposition technique, we have successfully prepared a‐axis oriented PrBa2Cu3−xNbxO7−z (PBCNO)(x=0–1.5) films and YBa2Cu3O7−x (YBCO)/PBCNO heterorepitaxial multilayer structures. For the PBCNO films, the resistivity showed semiconducting behavior at all Nb substitution levels investigated. The resistivity increased with increasing Nb content, reaching a value of 104 Ω cm at 100 K for a 300‐Å‐thick film with x=1.0. Using (100)SrTiO3 (STO) as a substrate, the following multilayer structures were successfully formed: (100)PBCNO(x=1.0)/(100)YBCO/(100)PBCO//STO, (001) YBCO/(100)PBCNO(x=1.0)/(100)PBCO//STO, and (100)YBCO/(100)PBCO/(100)PBCNO(x=1.0)/(100)PBCO//STO. The bottom and top YBCO layers in the (100)YBCO/(100)PBCO/(100)PBCNO/(100)PBCO/(100)YBCO//STO structure showed superconducting transition temperatures (zero resistance) of 82 and 83 K, respectively. The interlayer resistivity of the 200‐Å‐thick PBCNO(x=1) interlayer was as high as 105 Ω cm at 30 K.