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

Abstract Room temperature spin-dependent tunneling in Co/SiO x granular multilayers has been analysed by the frequency dependence of the impedance and tunnel magnetoimpedance. In the samples, layers of Co grains are separated by SiO x layers wich have different thickness for each sample. Mean relaxation times were determined from the complex impedance versus frequency curves using Cole–Cole fitting procedures. For a intermediary insulator thickness two spin-dependent modalities have been found. They are explained in terms of inter- and intra-plane tunnelling.