Anisotropic scattering effects in YBCO thin films

Magnetotransport studies of YBaCuO (YBCO) thin epitaxial films in the $ab$ plane have been performed. The studies were carried out for narrow rectangular bridges formed on the basis of YBCO films irradiated with helium ions. The dependences of the longitudinal and transverse voltages of the bridges on the external magnetic field $H$ were experimentally obtained for different temperatures $T$. As a result of processing experimental data, the behavior of the following quantities depending on ion fluence was studied: the superconducting critical temperature $T_c$, the mean free time $\tau$, concentration, and effective mass of free charge carriers. With a gradual increase in ion fluence, a crossover (transition) from the metallic behavior of films to the insulating behavior was experimentally observed. The behavior of the critical temperature $T_c$ as a function of $\tau$ is described using a model for $d$-wave superconductors with anisotropic impurity scattering. The anisotropic scattering parameter $g$ in YBCO films irradiated with helium ions has been determined. The $g$ parameters in films irradiated with helium ions and previously studied films irradiated with heavy ions, xenon, are compared. The correspondence of experimental results with theoretical predictions for $d$-wave superconductors is discussed.