Unusual metal-like state in HTSC and CMR oxides

Present report deals with the effect of disorder on Bi-2212 type high T-c superconducting and LCMO type CMR oxide materials. Ion irradiation (50 MeV Li3+ beam) creates high level of disorder in the superconducting system and as a result increase of room temperature resistivity (rho(300)) has been observed. Radiation induced point defects cause an increased d rho/d Tin the metal-like regime of Bi-2212. Similar increase of d rho/dT in the FM (ferromagnetic and metal-like) state has also been found in LCMO system. Enhancement of metal-like behavior is unusual in the sense that a simultaneous decrease of T-mi (metal-insulator transition temperature for LCMO) or T-c (superconducting transition temperature for Bi-2212) due to irradiation has also been observed. Effect of the defects incorporated by other means like variation of heat treatment and ion irradiation has been investigated for a better understanding on the electrical transport in these complex materials. Results have been discussed in the light of their intrinsic granular nature. (c) 2005 Elsevier B.V. All rights reserved.