Evolution of the GMR-effect amplitude in copper/permalloy-multilayered thin films

The evolution of the giant magnetoresistance (GMR) effect in thin film multilayers based on {Cu/Ni81Fe19}(N) has been investigated. The maximum effect amplitude at room temperature reaches about 20% and about 10% in first and second antiferromagnetic maximum, respectively. The magnetoresistance vs field dependence does not show a hysteresis. A simple magnetization reversal model has been applied to separate contributions of bilinear and biquadratic exchange energies to the magnetic coupling. It is shown, that this model can also be used to predict saturation fields for different systems. Multilayers with Cu layer thickness corresponding to the second maximum of the antiferromagnetic coupling survive heat spikes of up to 200 degrees C retaining their sensitivity of >0.16%/Oe. Investigations of multilayers comprised of blocks of first and second antiferromagnetic coupling maximum revealed the field dependence of the coupling between these blocks and it is shown that the GMR effect is simply additive. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.