Temperature dependence of spin waves in Co/CoO bilayers

Brillouin light scattering measurements of spin-wave frequencies in an exch ange coupled ferromagnet/antiferromagnet epitaxial Co/CoO bilayer are repor ted. A striking temperature dependence of the measured spin-wave frequencie s in the cobalt layer in the range 77-300 K was observed which has been dem onstrated to be due to exchange coupling to the ultrathin (7 Angstrom) CoO layer as antiferromagnetic order develops. The temperature dependence of th e spin-wave frequency demonstrates that interface exchange coupling occurs in the absence of the unidirectional anisotropy. A study of the mode line w idth shows a broadening with reducing temperature which indicates that loca lly ordered antiferromagnet regions persist above the Neel temperature and play a central role in determining the magnetic behavior of the bilayer sys tem. (C) 2001 American Institute of Physics.