Evidence for long localization length along b axis ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ in a axis ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$/a,b axis ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ superlattices

We have investigated resistive transitions of a axis ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$/a,b axis ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ superlattices in a magnetic field to study the correlation length of vortices along the a axis direction of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ across an a,b-axis oriented ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ barrier. The correlation of vortices across up to 480 Å of ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ is evidence consistent with long proximity coupling coherence lengths in ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ found in sandwich type ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$/${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$/${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ Josephson junctions. Investigation of a-b plane and b axis transport of undoped and cobalt doped ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ films suggests that a long localization length along the b axis of ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ is the origin of this long range proximity coupling.