Polarized neutron scattering from polycrystalline, exchange-biased magnetic multilayers

Specular reflection and off-specular scattering of polarized neutron has been used to study the magnetization reversal in polycrystalline [Ir20Mn80/Co80Fe20]N=3 exchange-biased multilayers. The reversal proceeds sequentially starting from the bottom (top) CoFe layer for decreasing (increasing) field. This behavior is related to the evolution of the grain size along the stack. The reversal of each CoFe layer is due to domain wall motions for both the decreasing and increasing field branch. The reversals are accompanied by fluctuations of the in-plane magnetization component perpendicular to the external field as evidenced by off-specular spin-flip scattering. The observed reversal mode is very similar to that of [Ir20Mn80/Co80Fe20]N multilayers with N=10 although the grain size decreases from N=3 to 10 by a factor of about four.