Polarized neutron reflectometry on a two-layer ME tape

Commercially available two-layer metal-evaporated videotape (composition Co 71Ni 16O 13) was brought into various remanent magnetic states by a wide recording head or by applying a perpendicular field. The polarized neutron reflectivity (PNR) of the tape in the various states has been measured. As PNR is sensitive to the magnetization as a function of depth, this technique enlarges the understanding of the writing process. The measurements were fitted simultaneously, keeping the nuclear structure the same for the different magnetic states. The model fitted to the measured data clearly shows two magnetic regions. It is also beyond doubt that the recorder head writes a signal through the whole depth of the tape. The model clearly shows the opposite easy axes in the in-plane direction of the separate layers after perpendicular magnetization.