Orientation and Superconducting Properties of REBa₂Cu₃O_y Thin Films Prepared by the Pulsed Laser Deposition Method

Abstract

Controlling the axis orientation in REBa₂Cu₃O_y (RE123; RE meaning Nd, Sm, Gd, Y and Yb) thin films is an important problem for many superconducting applications since RE123 materials have anisotropic properties (e.g., irreversible field, critical current density and so on) along their crystallographic axes. To obtain the RE123 thin films with excellent superconducting properties, we systematically studied the orientation, mechanism of orientation control and superconducting properties in RE123 thin films. We found that the preferred orientation of RE123 thin film on MgO and SrTiO₃ is c-axis orientation. RE123 thin films with RE/Ba substitution (RE=Sm, Gd) showed that the substrate temperature corresponding to the boundary line between the c-axis and a, c-axis mixed orientation decreased as RE/Ba substitution increased. These facts imply that the orientations of RE123 thin film are principally determined by their peritectic temperatures. The highest critical current densities of RE123 thin films so far are 7.93 MA/cm² for Sm123, 3.03 MA/cm² for Gd123 and 1.85 MA/cm² for Yb/Nd123.