Temperature dependent spin-wave behaviour in Co CoO bilayers

We report Brillouin light scattering measurements of spin-wave frequencies in an exchange coupled ferromagnet (FM)/antiferromagnet (AF) epitaxial fee Co/CoO bilayer structure. A striking temperature dependence of the measured frequencies in the cobalt layer in the range 77 to 300 K was observed and has been demonstrated to be due to exchange coupling to the antiferromagnetic layer. The existence of a uniaxial anisotropy field in the range 100-300 Oe within the AF layer along the FM magnetisation direction was demonstrated. The ratio of the interface to bulk AF exchange coupling strengths was found to lie in the range 0.75-1.1. The temperature dependence of the spin-wave line widths was also examined and used to show that locally ordered AF regions persist above the Neel temperature and play a central role in determining the magnetic behaviour. (C) 1999 Elsevier Science B.V. All rights reserved.