Defect induced enhancement of exchange bias by swift heavy ion irradiation in zinc ferrite-FeNiMoB alloy based bilayer films

Exchange biased systems consisting of ferromagnetic (FM)-antiferromagnetic (AFM) interfaces are increasingly being investigated because of their application potential in spin valves and tunnel junctions. In bilayer systems, ion irradiation is capable of modifying the interface and thereby offers unique opportunities to tailor exchange field. In the present study, irradiation with 100 MeV Ag8+ ions is utilized to alter the exchange bias field in zinc ferrite-FeNiMoB bilayer system. The thin films which were deposited by RF sputtering technique and annealed at 600 °C were irradiated at various fluences. Structural and magnetic studies were carried out by using Glancing X Ray Diffractometer (GXRD) and Superconducting Quantum Interference Device Vibrating Sample Magnetometer (SQUID VSM) respectively. It was observed that the as deposited films exhibited exchange bias and on ion irradiation, bias field could be enhanced at certain fluences. The enhancement in bias field is attributed to defects created in the antiferromagnet as a result of ion irradiation. The experimental result is fitted in accordance with the diluted antiferromagnet model. Coercivity was also found to vary with ion fluence. Ion fluence was thus effectively used to enhance bias field as well as coercivity in the bilayer consisting of zinc ferrite-FeNiMoB.