Magneto-optical study of exchange-biased sputtered Co/CoO films

We investigate the magnetic properties of sputtered Co/CoO films. Field cooling the samples causes a negative shift of the hysteresis loops below a characteristic temperature, dependent on the growth conditions (choice of the substrate, bilayer thickness, oxidation procedure), which is sensibly lower than the Neel temperature of bulk antiferromagnetic CoO, indicating a granular structure of the oxide layer. However, the maximum observed value of the exchange bias field is larger than what obtained in well-controlled epitaxial films reported in the literature. (C) 2003 Elsevier B.V. All rights reserved.