Microstructure and magnetic properties of sputtered spin valve systems

Different sputtering methods, viz. rf-diode, rf-magnetron, and dc-magnetron sputtering, have been used to increase the sensitivity of Co/Cu/Co/FeMn top spin valve systems by more than a factor of 2. This improvement is due to an enhanced magnetoresistive effect ΔR/R and a reduced anisotropy field Hk for the best sample. In the present paper the transport and magnetic properties are discussed in the context of microstructure and interfacial quality of the multilayers evaluated by comprehensive transmission electron microscopy and x-ray reflectometry investigations. The sample with the highest sensitivity (dc-magnetron sputtered) shows less structural defects and locally smoother interfaces than the other samples. Additionally it is shown that the ferromagnetic interlayer exchange field is not affected by the applied sputtering methods and can be well understood in terms of orange peel coupling.