Effect of 200Â MeV Ag15+ ion irradiation on structural and electrical transport properties of Fe3O4 thin films

Thin films of Fe3O4 have been deposited on single crystal MgO(1 0 0) and Si(1 0 0) substrates using pulsed laser deposition. Films grown on MgO substrate are epitaxial with c-axis orientation whereas, films on Si substrate are highly 〈1 1 1〉 oriented. Film thicknesses are 150 nm. These films have been irradiated with 200 MeV Ag ions. We study the effect of the irradiation on structural and electrical transport properties of these films. The fluence value of irradiation has been varied in the range of 5 × 1010 ions/cm2 to 1 × 1012 ions/cm2. We compare the irradiation induced modifications on various physical properties between the c-axis oriented epitaxial film and non epitaxial but 〈1 1 1〉 oriented film. The pristine film on Si substrate shows Verwey transition (TV) close to 125 K, which is higher than generally observed in single crystals (121 K). After the irradiation with the 5 × 1010 ions/cm2 fluence value, TV shifts to 122 K, closer to the single crystal value. However, with the higher fluence (1 × 1012 ions/cm2) irradiation, TV again shifts to 125 K.