Angular Magnetoresistivity Measurements in the Pseudogap Region of $Y_{1-x}Pr_{x}Ba_{2}Cu_{3}O_{7-\delta}$

We carried out a detail investigation of the angular dependence of in-plane conductivity $\sigma_{ab}(\theta)$ ($\theta$ is the angle between the direction of H and c-axis of the sample) near and above the zero field critical temperature $T_{c0}$ of $Y_{1-x}Pr_{x}Ba_{2}Cu_{3}O_{7-\delta}$ single crystals for applied magnetic field H up to 14 T. We studied a large range of Pr concentrations x; i. e. $0.20 \leq x \leq 0.53$. We write the total in-plane conductivity as the sum of quasiparticle and flux-flow type contributions. This expression fits very well the data in the pseudogap region up to a temperature $T_{\phi}$ ($T_{c0} < T_{\phi} < T^{*}$, where $T^{*}$ is the pseudogap temperature) and for all values of H. Above $T_{\phi}$, the quasiparticle component alone is able to fit the data perfectly. These results clearly indicate the presence of vortex like contribution to dissipation above $T_{c0}$. The temperature and magnetic field dependence of the three fitting coefficients will also be discussed. A plot of the $T_{\phi}$ $vs$ $x$ phase diagram is compared with the corresponding $T_{c0}(x)$ in order to show the extent of $T_{\phi}$ above $T_{c0}$. The ratio of $T_{\phi}/T_{c0}$ increases with increasing x doping.