Competing spin-dependent conductance channels in underoxidized tunnel junctions

Abstract

The authors study the transport properties of magnetic tunnel junctions (MTJs) with underoxidized 9 Å Al Ox barriers suitable for magnetoresistive sensors in high-density storage devices. Temperature dependent measurements revealed different dominant transport mechanisms in different junctions: tunnel, metallic, or both, depending on the MTJ-magnetic state. This denotes a competition between two conductance channels (tunnel through oxidized Al Ox and metallic through unoxidized Al nanoconstrictions), so that the dominance of one over the other is the outcome of small structural and composition variations in the barrier. Furthermore, transport through the Al nanobridges is spin dependent, caused by ballistic and/or diffusive magnetoresistance through nonmagnetic metallic paths. © 2007 American Institute of Physics.