Magnetization profile in antiferromagnetically coupled recording media

We report polarized neutron reflectivity (PNR) studies of antiferromagnetically coupled (AFC) magnetic recording media with the aim of understanding how the two ferromagnetic layers switch magnetization direction. The PNR measurements were conducted at applied magnetic fields from near saturation to near the coercive field of the upper layer. From the PNR spectra, we obtain the magnetization profile of the AFC media. The results verify that the lower layer is aligned antiparallel to the magnetically hard upper layer in low fields. However, the magnetization of the upper layer shows an unexpected decrease as the lower layer reverses direction, which indicates that the interaction between the upper and lower layers is more complex than previously thought.