Correlation between the residual resistivity ratio and the power-law of the normal-state resistivity in MgB₂

MgB₂ polycrystalline superconducting specimens were irradiated with several doses of γ-rays up to 100 MR. An increase in the normal state resistivity and a broadening of the resistive transition to the superconducting state were observed with increasing γ-irradiation dose. Although very small changes to the superconducting transition temperature were obtained after y-irradiation, different temperature dependence of normal-state resistivity and different residual resistivity ratios, RRR were obtained for different doses. We have found a correlation between RRR and the power law dependence of resistivity, n as the irradiation dose increases. This correlation may be an indication that the electron-phonon interaction is important in these samples. These results are attributed to the disorder caused by y-rays.