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 γ‐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 γ‐rays. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)