Agradecimentos: The authors are thankful to the Director and Pelletron Group of Inter-University Accelerator Centre, New Delhi for providing the necessary characterization and irradiation facilities. This work was supported by the Korean Research Foundation Grant funded by the Korea Government (MOEHRD) (KRF – 2008 – 005 – J02703). Authors (SKS & MK)) are very grateful to FAPESP and CNPq (Brazil) for providing financial support (Grant No.06/06792-2) Ver menos

Abstract: Nanocrystalline Mg0.95Mn0.05Fe2O4 ferrite thin films, prepared by pulsed laser deposition technique on a glass substrate coated with indium tin oxide, are irradiated with 200 MeV Ag15+ ions at different fluence values in the range from 1 x 10(11) to 1 x 10(12) ions/cm(2). The as-deposited and irradiated thin films are investigated using X-ray diffraction, dc magnetization and atomic force microscopy techniques. X-ray diffraction analysis of the as-deposited as well as irradiated thin film indicates the single phase cubic structure as the main composition. The crystallite size evaluated from Scherrer's equation is found to be decreased from 26 nm for as-deposited thin films to 17 nm for irradiated at a fluence of 1 x 10(12) ions/cm(2). The decrease in crystallite size in all the thin film samples after irradiation indicates a distortion in the lattice structure caused by stress-induced defects. The zero-field-cooled (ZFC) and field-cooled (FC) magnetizations have been recorded in a low field of 100 Oe and they show a typical behavior of superparamagnetic particles. This is further supported by the magnetization hysteresis (M-H) curve taken at 300 K, for the as-deposited thin film, which shows zero coercivity and remanence. The blocking temperatures calculated from the maxima of ZFC are found to decrease with the increase in irradiation fluence, which is consistent with XRD results Ver menos