Enhanced $J_{c}$ in $\hbox{\rm YBa}_{2}\hbox{\rm Cu}_{3}\hbox{O}_{7 - \delta}$ Thin Films by Low-Level Cr Doping
<formula formulatype="inline"><tex Notation="TeX">$\hbox{YBa}_{2}(\hbox{Cu}_{1 - {\rm x}}\hbox{Cr}_{\rm x})_{3}\hbox{O}_{7 - \delta}$</tex></formula> (<formula formulatype="inline"><tex Notation="TeX">${\rm x} = 0$</tex></formula>, 0.02%, 0.04%, 0.06%) thin films were prepared by trifluoroacetate metal organic deposition on <formula formulatype="inline"><tex Notation="TeX">$ \hbox{LaAlO}_{3}$</tex></formula> (001) single crystal substrates. Critical current density and irreversibility field were correspondingly improved distinctly by Cr doping. Analysis suggested that the pinning type was <formula formulatype="inline"><tex Notation="TeX">$\delta l$</tex></formula> pinning for all derived thin films, and the dominant pinning type was not shifted to <formula formulatype="inline"><tex Notation="TeX">$\delta T_{c}$</tex></formula> 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.