Sequence, symmetry, and magnetic fluctuations of the magnetization reversal in exchange-biased multilayers

The magnetization reversal in [Ir{sub 20}Mn{sub 80}/Co{sub 80}Fe{sub 20}]{sub 10} exchange-biased multilayers is studied by specular reflection and off-specular scattering of polarized neutrons. The reversal proceeds sequentially starting with the bottom (top) CoFe layer for decreasing (increasing) field due to the evolution of the grain size along the stack. Each CoFe layer remagnetizes symmetrically for both field branches in a nonuniform mode. Concomitant in-plane magnetization fluctuations revealed by off-specular spin-flip scattering indicate a more complex reversal mechanism than hitherto considered.