Impurity effects on the normal-state transport properties of Ba sub(0.5) K sub(0.5) Fe sub(2) As sub(2) superconductors

We investigated the normal-state resistivity [rho]xx (T) and the Hall effect in Zn- and Co-doped Ba sub(0.5) K sub(0.5) Fe sub(2) As sub(2) single-crystalline microbridges. A crossover temperature T* was observed in the temperature dependency of the longitudinal resistivity [rho]xx (T), which separates [rho]xx (T) into temperature-linear and temperature-nonlinear regions. Above T*, the carriers in Ba sub(0.5) K sub(0.5) Fe2 As sub(2) and Co-doped Ba sub(0.5) K sub(0.5) Fe sub(1.94) Co sub(0.06) As sub(2) demonstrate electronlike behavior and an anomalous nonlinear magnetic field dependence of the Hall voltage with a sign reversal. By contrast, the Zn-doped Ba sub(0.5) K sub(0.5) Fe sub(1.94) Zn sub(0.06) As sub(2) behaves like a hole type and the Hall coefficient is independent of the magnetic field. The field-induced sign reversal of the Hall coefficient of undoped and Co-doped samples depends on the field modification on the mobility and hole/electron concentration ratio. The T super(2)-dependent Hall angle of a nonmagnetic Zn-doped crystal is observed as a nearly parallel shift from that of the impurity-free crystal in the low-temperature region, indicating that the Zn induces a weak change of the spinons excitations, while increasing the number of scattering centers. The Co works as a nonmagnetic impurity as well, while it provides both spinons excitations and impurity scattering.