Swift heavy ion irradiation effects on transport properties of epitaxial thin films of La1-xCaxMnO3

The influence of swift heavy ion (SHI) irradiation on transport properties of epitaxial thin films of La0.75Ca0.25MnO3 (LCMO) is studied. The films were irradiated with 90 MeV O-16 beams and 250 MeV Ag-107 beams at different fluence values. In the case of 90 MeV O-16 ions LCMO specimens were irradiated to 10(11)-10(14) ions/cm(2) and for 250 MeV Ag-107 ions with 10(10)-10(13) ions/cm(2). A systematic variation in Curie temperature (T-c) or resistivity peak temperature (T-p) has been observed. It has been noted that for both types of ions the T-p increased for the specimen irradiated at 10(11) ions/cm(2) fluence. Further increase of fluence decreased the T-p value and at higher fluence (10(14) ions/cm(2) for 90 MeV O-16 and 10(13) ions/cm(2) for 250 MeV Ag-107 ions) the specimens showed no metal-to-insulator transition even at low temperature down to 77 K. They show completely semiconducting behavior with high resistance values. These results are discussed in terms of SHI irradiation-induced structural distortion and strain on thin films.