Radiation damage effects on transport and colossal magnetoresistance in La(1-x)CaxMnO3

The effects of crystal lattice disorder induced by irradiation of La-Ca-Mn-O films are reviewed. These experiments provide insight into the anomalous transport properties and colossal magnetoresistance (CMR) of these perovskites. Electron irradiation produces only slight lattice damage, about 10-5 displacements per atom (dpa) which would be imperceptible in an ordinary bad metal or activated semiconductor but gives large changes in resistance that illustrate the exotic nature of transport in both the metallic and insulating phases of the CMR films. Ion irradiation produces damage ranging from 5 x 10-3 dpa to 2.4 x 10-2 dpa which provides a systematic picture of CMR and transport from relatively small lattice disorder to more severe disorder, sufficient to completely suppress the metal-insulator (M-I) transition