Intra and inter-plane spin dependent tunneling in Co/SiOx granular multilayers

Room temperature spin-dependent tunneling in Co/SiOx granular multilayers h as been analysed by the frequency dependence of the impedance and tunnel ma gneto impedance. In the samples. layers of Co grains are separated by SiOx layers wich have different thickness for each sample. Mean relaxation times were determined from the complex impedance versus frequency curves using C ole-Cole fitting procedures. For a intermediary insulator thickness two spi n-dependent modalities have been found. They are explained in terms of inte r- and intra-plane tunnelling. (C) 2001 Elsevier Science B.V. All rights re served.