Magnetic properties of exchange-biased FeCo/CoO bilayer and its electronic structure

Magnetic and structural properties of FeCo/CoO bilayer prepared by ion beam sputtering on silicon substrate have been studied. As-deposited specimen exhibits exchange bias at 10 K. The influence of thermal annealing and swift heavy ion on the exchange bias field has been studied. Thermal annealing enhances the value of exchange bias field (HEB) as well as magnetic moment of the bilayer; revealing that the exchange bias value is tailored by the thermal annealing and depends upon annealing temperature. X-ray diffraction gives convincing support of the phase formation of Co3O4 in the CoO layer after thermal annealing. A correlation has been observed between soft X-ray absorption and the corresponding magnetic characteristics. The exchange bias effect exists up to temperatures beyond the ordering temperature of the Cobalt oxide layer. Upto the 6 × 1013 ions/cm2of 100 MeV Au-ion irradiation does not change the magnetization behaviour of the FeCo/CoO system. Higher ion fluence of 1 × 1014 Au-ions/cm2, reduces the HEBvalue. Thermal annealing enhances the HEB value. From the soft X-ray absorption, it reveals that the reduction in the HEB value for the ion-irradiated specimen is due to defects present in the film.