Enhanced $J_{c}$ in $\hbox{\rm YBa}_{2}\hbox{\rm Cu}_{3}\hbox{O}_{7 - \delta}$ Thin Films by Low-Level Cr Doping

$\hbox{YBa}_{2}(\hbox{Cu}_{1 - {\rm x}}\hbox{Cr}_{\rm x})_{3}\hbox{O}_{7 - \delta}$
(
${\rm x} = 0$
, 0.02%, 0.04%, 0.06%) thin films were prepared by trifluoroacetate metal organic deposition on
$ \hbox{LaAlO}_{3}$
(001) single crystal substrates. Critical current density and irreversibility field were correspondingly improved distinctly by Cr doping. Analysis suggested that the pinning type was
$\delta l$
pinning for all derived thin films, and the dominant pinning type was not shifted to
$\delta T_{c}$
pinning by Cr doping. Combined with the result that the critical superconducting temperature was not depressed by Cr doping, it was concluded that Cr probably occupied into the Cu(1) sites.