Effects of Zn doping on the anisotropic penetration depth of Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$

We have investigated the temperature ($T$) and doping dependences of the anisotropic magnetic penetration depth $\lambda$ of high-quality grain-aligned $\mathrm{Y}{\mathrm{Ba}}_2{\left({\mathrm{Cu}}_{1-x}{\mathrm{Zn}}_x\right)}_3{\mathrm{O}}_7$ with $x=0.00, 0.02, 0.03, \mathrm{and} 0.05$ using the ac-susceptibility technique. The values of the in-plane ${\lambda }_{\mathrm{ab}}\mathrm{}\left(0\right)\mathrm{}$, and out-of-plane, ${\lambda }_c\mathrm{}\left(0\right)\mathrm{}$, penetration depths were found to increase strongly with increased Zn concentration whereas the anisotropy ratio $\gamma =\left[\frac{{\lambda }_c\mathrm{}\left(0\right)\mathrm{}}{{\lambda }_{\mathrm{ab}}\mathrm{}\left(0\right)\mathrm{}}\right]$ decreased. With increased Zn doping the ${\left[\frac{{\lambda }_{\mathrm{ab}}\mathrm{}\left(0\right)\mathrm{}}{{\lambda }_{\mathrm{ab}}\mathrm{}\left(T\right)\mathrm{}}\right]}^2$ and ${\left[\frac{{\lambda }_c\mathrm{}\left(0\right)\mathrm{}}{{\lambda }_c\mathrm{}\left(T\right)\mathrm{}}\right]}^2$ curves systematically approach each other.