Comparative study between the effect of annealing and substrate temperature on the magnetic and transport properties of Co20Cu80 granular alloys

We have studied the effect of substrate temperature on the magnetic and the transport properties and compared it to the results of annealing in Co20Cu 80 granular alloy. The samples were prepared by ion-beam sputtering techniq ue (IBS). At room temperature, the optimal value of the giant magnetoresist ance (GMR) is observed in Co20Cu80 alloy after annealing at 250 degreesC. H owever, the substrate temperature was found to have an opposite effect when compared to the results of the annealing. Indeed, as the substrate tempera ture increases the GMR decreases down to about 0.3%. Moreover, the saturati on, field is decreasing to reach approximately 2 kOe for 350 degreesC subst rate temperature. Such a reduction of the saturation field is not generally observed in the Co-Cu granular alloys prepared by other techniques. This i s attributed to the fact that the CoCu alloys deposited at high substrate t emperature have an appreciable mobility of their particles and favoured a q uasi complete segregation with large grains size. (C) 2001 Elsevier Science B.V. All rights reserved.