Defects induced magnetic transition in Co doped ZnS thin films: Effects of swift heavy ion irradiations

The effect of swift heavy ions (SHI) on magnetic ordering in ZnS thin films with Co ions substituted on Zn sites is investigated. The materials have been synthesized by pulsed laser deposition on substrates held at 600 degrees C for obtaining films with wurtzite crystal structure and it showed ferromagnetic ordering up to room temperature with a paramagnetic component. 120 MeV Ag ions have been used at different fluences of 1 x 10(11) ions/cm(2) and 1 x 10(12) ions/cm(2) for SHI induced modifications. The long range correlation between paramagnetic spins on Co ions was destroyed by irradiation and the material became purely paramagnetic. The effect is ascribed to the formation of cylindrical ion tracks due to the thermal spikes resulting from electron-phonon coupling. (C) 2012 Elsevier B.V. All rights reserved.