Training effects and the microscopic magnetic structure of exchange biasedCo/CoO bilayers

Exchange bias of a partially oxidized thin film of ferromagnetic Co was stu died by magnetization measurements and polarized neutron reflectivity (PNR) . The magnetization curve shows strong effects of training with cycling of the magnetic field. Reflectivity measurements with the field parallel to th e cooling field showed the onset of spin-dependent diffuse scattering-off t he specular reflection-after a training cycle. Such scattering, of the Yone da type, is due to misaligned Co domains possibly close to the Co/CoO inter face. Subjecting the field cooled Co/CoO pair to a field perpendicular to t he cooling field causes a rotation of the magnetization. The PNR measuremen ts confirmed earlier susceptibility studies by indicating that the rotation of the magnetization is reversible in fields up to 400 Oe. The rotation of the magnetization of Co is uniform across the film thickness. (C) 2000 Ame rican Institute of Physics. [S0021-8979(00)59008-2].