Effects of the Internal strain on the magnetic differential permeability and the stress sensitivity in Co/Cu multilayers

Co/Cu multilayers were produced by means of sputtering in order to obtain a constant Co layer thickness while the Cu interlayers had variable thicknesses. The Cu layer thickness was always greater than 15 Angstrom in order to produce magnetically decoupled Co adjacent layers. We have observed that by varying the Cu layer thickness an effect is produced on both the magnetic differential permeability and the stress sensitivity in the plane of the films. In particular, the differential permeability is reduced upon increasing the Cu interlayer thickness and the stress sensitivity displays a maximum as a function of the applied compressive stress. The effects are tentatively interpreted in terms of the presence of a coherent interface between adjacent layers. By relating the maximum in the stress sensitivity to the average internal stress, we have evaluated the interface thickness.