Enhanced $J_{c}$ in $\hbox {\rm YBa}_{2}\hbox {\rm Cu}_{3}\hbox {O}_{7 - \delta }$ Thin F

$\hbox {YBa}_{2}(\hbox {Cu}_{1 - {\rm x}}\hbox {Cr}_{\rm x})_{3}\hbox {O}_{7 - \delta }$ ( ${\rm x} = 0$ , 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.