Coexistence of positive and negative exchange bias in CrMn/Co bilayers

Exchange-biased CrMn/Co bilayers with various thicknesses of Co sputtered onto Si(100) substrates by the RF sputtering system have been studied. Double-shifted loops have been observed with the thickness of Co layer in a narrow range and become single-shifted loops after some cycles of measurement. Those results are interpreted as the association of positive and negative exchange bias. (C) 2005 Elsevier B.V. All rights reserved.