Scaling of resistivities and guided vortex motion in MgB2 thin films

Longitudinal and transverse voltages have been measured on thin films of MgB2 with different superconducting transition widths. The study has been performed in zero and non-zero external magnetic fields. The non-zero transverse voltage has been observed in close vicinity of the critical temperature in zero external magnetic field, while further away from Tc this voltage becomes zero. In a magnetic field it becomes a transverse voltage which is an even function with respect to the direction of the field. The usual Hall voltage starts to appear with increasing magnetic field and in large fields the even voltage disappears and only the Hall voltage is measurable (i.e. the transverse even voltage is suppressed with increasing magnetic field and increasing transport current). New scaling between transverse and longitudinal resistivities has been observed in the form ρxy∼dρxx/dT. This correlation is valid not only in the zero magnetic field but also in the non-zero magnetic field where transverse even voltage is detected. Several models trying to explain the observed results are discussed. The most promising one seems to be guided motion of the vortices, though further theoretical work will be required to confirm this.