Magnetization processes in double-layer films for perpendicular recording

We examine the influence of the NiFe underlayer on the magnetization reversal processes of CoCr films by rotational hysteresis measurements. We analyse both the case of the NiFe film deposited over the CoCr layer and the case of the CoCr film deposited over the NiFe layer. In the first case no appreciable variations occur for the switching process of the CoCr film with respect to the case of a single layer of CoCr. In the second case the rotational losses of the CoCr layer increase with respect to the single CoCr layer ones for both in plane and perpendicular rotations. The rotational hysteresis integral increases in case of perpendicular rotation. These results indicate that, when the CoCr is deposited over the NiFe layer, the reversal mechanism of CoCr becomes "more incoherent". This effect is ascribed to the enhancement of the influence of the CoCr "initial layer" (which is in contact with the NiFe substratum) on the top layer of CoCr. © 1989.