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 antiferromagnet ic layer. The existence of a uniaxial anisotropy field in the range 100-300 Oe within the AF layer along the FM magnetisation direction was demonstrat ed. The ratio of the interface to bulk AF exchange coupling strengths was f ound to lie in the range 0.75-1.1. The temperature dependence of the spin-w ave 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 deter mining the magnetic behaviour. (C) 1999 Elsevier Science B.V. All rights re served.