Structural, electrical transport, magnetization, and 1/f noise studies in 200 MeV Ag Ion irradiated La _0.7Ce _0.3MnO ₃ thin films

The effect of 200 MeV Ag ion irradiation on structural, electrical transport, magnetization, and low-frequency conduction noise properties of electron-doped La _0.7Ce _0.3MnO ₃ thin films have been investigated. The as-grown thin films show c-axis epitaxial structure along with a small amount of unreacted CeO ₂ phase. After the irradiation, at the lowest fluence both the magnetization and metal-insulator transition temperature increase. Further increase in fluence reduces the metal-insulator transition temperature and leads to larger resistivity; however, the unreacted phase of CeO ₂ disappears in the x-ray diffraction pattern. On the other hand, the normalized electrical noise is greatly enhanced even at the lowest nonzero fluence. Surprisingly the conducting noise in the irradiated samples is much higher in the metallic state than in the semiconducting one. The observed modifications in structural, electrical, magnetic, and noise properties of 200 MeV Ag ion irradiated La _0.7Ce _0.3MnO ₃ thin films have been explained on the basis of effects of the presence of swift heavy-ion irradiation-induced strain and defects.