Giant magnetoresistance in Co-Ag granular films prepared by low-energy cluster beam deposition

In this paper, we report on structural, magnetic, and magnetoresistive properties of Co-Ag granular films made by low-energy cluster beam deposition (LECBD). With this technique, we can grow granular films of cobalt clusters embedded in silver or other matrix materials, with independent control of the size and concentration of the clusters. Moreover, we show, from TEM, grazing-incidence small-angle x-ray diffraction, and magnetic measurements, that the size of the clusters is the same, whatever the matrix. We measured the giant magnetoresistance (GMR) and magnetic properties of cobalt clusters in silver, and found them similar to those of granular alloys made by codeposition of atoms. Then, taking advantage of the independent control on the size and distribution of the clusters allowed with LECBD, we studied the concentration dependence of the GMR. Its variation at low cobalt content seems to indicate that GMR in the granular geometry is intermediate between CLP and CPP.