SPIN-DEPENDENT TUNNELING IN DISCONTINUOUS METAL INSULATOR MULTILAYERS/

We have studied the structural, magnetic and transport properties of ( Co/SiO2) discontinuous multilayers. These multilayers consist of layer s of Co particles embedded in an insulating SiO2, matrix. The current- in-plane (CIP) and current-perpendicular-to-the-plane (CPP) resistivit ies of the discontinuous multilayers can be tuned independently over o rders of magnitude by varying the nominal thicknesses of the metallic and insulating layers. Negative magnetoresistance (MR) due to spin-dep endent tunneling has been observed in both CIP and CPP geometries, At room temperature the two magnetoresistive responses are similar, diffe ring only in magnitude. At lower temperatures, the two responses are r emarkably different. The CIP-MR saturates readily following the magnet ization curve whereas the CPP-MR exhibits hysteresis up to magnetic fi elds higher than 20 kOe. These differences suggest the nature of the m agnetic domain structure in each metallic plane. These systems should permit a combination of ease in preparation with high magnetoresistanc e sensitivity at low fields. (C) 1998 Elsevier Science B.V. All rights reserved.