Three-state memory combining resistive and magnetic switching using tunnel junctions

Abstract

Magnetic fields generated by current lines are the standard way of switching between resistance (R) states in magnetic random access memories. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current crossing the tunnel barrier. Such current induced magnetization switching (CIMS) or current induced switching (CIS) effects were recently observed in thin magnetic tunnel junctions, and attributed to spin transfer (CIMS) or electromigration of atoms into the insulator (CIS). In this work, electromigration-driven resistance changes (resistive switching) are superimposed with thermally induced pinned layer reversal (magnetic switching), producing a reproducible, three-state memory device. The tunnel junctions under study show a tunnel magnetoresistance of 14% with a RA product of 50 Ω νm2. The reversible electromigration-driven resistance changes amount to 7-8% of the full resistance change and more than 104 R-switching events can be current induced without significant damage to the tunnel junction. Typical critical current densities are of the order of 2 × 106 A cm-2. © 2007 IOP Publishing Ltd.